Vanadium compounds for treating cancer

ABSTRACT

The invention provides methods for treating cancer and compounds that are useful for the treatment of tumors, as well as pharmaceutical compositions comprising the compounds, and synthetic methods and intermediates useful for preparing the compounds.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of application Ser. No. 10/857,440, filed May 28, 2004, which is a divisional of application Ser. No. 10/142,305, filed May 8, 2002, now U.S. Pat. No. 6,743,786, which is a divisional of application Ser. No. 09/378,531, filed Aug. 20, 1999, now U.S. Pat. No. 6,432,941, which claim priority to provisional application Ser. No. 60/097,377, filed Aug. 21, 1998 and is a continuation-in-part of application Ser. No. 09/187,115, filed Nov. 5, 1998, now U.S. Pat. No. 6,245,808 and a continuation-in-part of application Ser. No. 09/008,898, filed Jan. 20, 1998, now U.S. Pat. No. 6,051,603, which applications are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to Vanadium (IV) compounds effective for treating tumor cells and particularly effective to induce apoptosis in leukemia cells, breast cancer cells, prostate cancer cells, and brain cancer cells.

BACKGROUND OF THE INVENTION

Cancer is a major disease that continues as one of the leading causes of death at any age. In the United States alone, it is anticipated that more than half a million Americans will die of cancer in 1999. Currently, radiotherapy and chemotherapy are two important methods used in the treatment of cancer.

Considerable efforts are underway to develop new chemotherapeutic agents for more potent and specific anti-cancer therapy, presenting effective and efficient cytotoxicity against tumor cells, with minimal interference with normal cell function. Accordingly, there is an urgent need for the development and analysis of novel, effective anti-cancer agents.

A single vanadocene (IV) compound (e.g., VCp₂Cl₂) is reported as having biological activity.

Sakurai, et. al, BBRC, Vol. 206, p. 133 (1995) discloses an oxovanadium compound (e.g., [VO(Phen)(H₂O₂](SO₄)) that is active against pharyngonasal cancer as determined by a single assay.

Holmes, Ph.D. Thesis, LSU (1961) discloses oxovanadium compounds (e.g., [VO(SO₄)(Phen)₂] and [VO(ClO₄)(Bpy)₂]) but does not disclose biological data for the compounds.

Selbin, Chem. Rev., Vol. 65, p. 155 (1965) discloses oxovanadium compounds (e.g., [VO(SO₄)(Phen)₂] and [VO(ClO₄)(Bpy)₂]) but does not disclose biological data for the compounds.

SUMMARY OF THE INVENTION

The invention provides a method for treating cancer in a mammal comprising administering to the mammal in need of such treatment an effective amount of a vanadium (IV) compound; or a parmaceutically acceptable salt thereof; with the proviso that the vanadium (IV) compound is not VCp₂Cl₂ or [VO(Phen)(H₂O)₂](SO₄).

The invention also provides a method for treating a mammal inflicted with cancer comprising administering to the mammal in need of such treatment an effective amount of an oxovanadium compound; or a pharmaceutically acceptable salt thereof; with the proviso that the cancer is not pharyngonasal cancer.

The invention also provides a method for treating a mammal inflicted with cancer comprising administering to the mammal in need of such treatment an effective amount of a vanadocene compound; or a pharmaeutically acceptable salt thereof; with the proviso that the vanadocene compound is not VCp₂Cl₂.

The invention also provides a compound of formula II:

wherein R and R¹ are each independently H, (C1-C3)alkyl, halogen, (C1-C3)alkoxy, halo(C1-C3)alkyl, cyano, (C₂-C₆)alkanoyloxy or nitro; X and X¹ are each independently a monodentate or bidentate ligand, or no ligand is present on X₁; and Y is a monodentate ligand; or a pharmaceutically acceptable salt thereof; with the proviso that the compound is not [VO(SO₄)(Bpy)₂].

The invention also provides a compound of formula III:

wherein R²and R³ are each independently H, (C1-C3)alkyl, halogen, (C1-C3)alkoxy, halo(C1-C3)alkyl, cyano, (C₂-C₆)alkanoyloxy or nitro; X² and X³ are each independently a monodentate or bidentate ligand, or no ligand is present on X³; and Z is O, CH₂, CH₂—CH₂ or CH═CH; or a pharmaceutically acceptable salt thereof; with the proviso that the compound is not [VO(Phen)(H₂O)₂](SO₄) or [VO(SO₄)(Phen)₂].

The invention also provides a compound of formula IV:

wherein R⁴, R⁵ and R⁶ are each independently H, (C1-C3)alkyl, halogen, (C1-C3)alkoxy, halo(C1-C3)alkyl, cyano, (C₂-C₆)alkanoyloxy or nitro; X⁴ and X⁵ are each independently a monodentate or bidentate ligand, or no ligand is present on X⁵; Y is a monodentate ligand, or no ligand is present on X⁵; and Y is a monodentate ligand; or a pharmaceutically acceptable salt thereof; with the proviso that the compound is not [VO(Phen)(H₂O)₂](SO₄) or [VO(SO₄)(Phen)₂].

The invention also provides a compound of formula V:

wherein R⁷ and R⁹ are each independently H, (C1-C3)alkyl, (C1-C3)alkoxy, or halo(C1-C3)alkyl; R⁸ is H, (C1-C3)alkyl, halo, (C1-C3)alkoxy, or halo(C1-C3)alkyl; Y and Y¹ are each independently a monodentate or bidentate ligand; and n is 0 or 1; or a pharmaceutically acceptable salt thereof.

The invention also provides a compound of formula VII:

wherein R¹ and R² are each independently a cyclopentadienyl ring, wherein any cyclopentadienyl ring may optionally be substituted with one or more (C₁-C₃)alkyl; and R¹⁰-R¹³ are each independently H, halo, or (C1-C6)alkyl; or a pharmaceutically acceptable salt thereof.

The invention also provides a pharmaceutical composition comprising a compound of formula II:

wherein R and R¹ are each independently H, (C₁-C₃)alkyl, halogen, (C₁-C₃)alkoxy, halo(C1-C3)alkyl, cyano, (C₂-C₆)alkanoyloxy or nitro; X and are each independently a monodentate or bidentate ligand; or no ligand is present on X¹; and Y is a monodentate ligand, or no ligand is present on X¹; and Y is a monodentate ligand or a pharmaceutically acceptable salt thereof; and a pharmaceutically acceptable carrier.

The invention also provides a pharmaceutical composition comprising a compound of formula III:

wherein R² and R³ are each independently H, (C1-C3)alkyl, halogen, (C1-C3)alkoxy, halo(C1-C3)alkyl, cyano, (C₂-C₆)alkanoyloxy or nitro; X² and X³ are each independently a monodentate or bidentate ligand, or no ligand is present on X³; and Z is O, CH₂, CH₂—CH₂ or CH═CH; or a pharmaceutically acceptable salt thereof; and a pharmaceutically acceptable carrier; with the proviso that the compound is not [VO(Phen)(H₂O)₂](SO₄).

The invention also provides a pharmaceutical composition comprising a compound of formula IV:

wherein R⁴, R⁵ and R⁶ are each independently H, (C1-C3)alkyl, halogen, (C1-C3)alkoxy, halo(C1-C3)alkyl, cyano, (C₂-C₆)alkanoyloxy or nitro; X⁴ and X⁵ are each independently a monodentate or bidentate ligand, or no ligand is present on X⁵; Y is a monodentate ligand; or a pharmaceutically acceptable salt thereof; and a pharmaceutically acceptable carrier; with the proviso that the compound is not [VO(Phen)(H₂O)₂](SO₄).

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1. Illustrates cytotoxic activity of vanadocenes on human testicular cancer cell lines with (A) Tera-2 cells and (B) Ntera-2 cells. Cells were incubated with increasing concentrations (1.9 μM-250 μM) of 5 representative vanadocenes, VDOCN, VDSCN, VDSeCN, VDT, and VD(dtc) in DMSO for 24 hr in 96-well plates and the cell survival was determined by the MTT assay as described in materials and methodsActivity is expressed relative to DMSO controls. The data points represent the mean value of triplicates. The SD for each compound was <5% of the mean values.

FIG. 2. Illustrates VDSeCN and VDSCN induce apoptosis in human testicular cancer cells. (Left panels) TUNEL analysis: Two-color flow cytometric contour plots of Ntera-2 cells treated with and without vanadocenes. Cells were incubated for 24 h in either control medium (0.1% DMSO) [A], or in medium supplemented with 100 μM VDSCN [B] or VDSeCN [C] in 0.1% DMSO, fixed, permeabilized, and visualized for DNA-fragmentation in a TUNEL assay using TdT and FITC-dUTP. Red fluorescence represents nuclei counterstained with propidium iodide. Percentages indicate cells with increased dUTP incorporation. (Right panels) Confocal images: Two-color confocal laser scanning microscopy images of control and apoptotic cells. B) Control cells visualized for dUTP incorporation using FITC-dUTP. D and F) Apoptotic nuclei of cells treated with VDSCN and VDSeCN are recognized by fluorescein labeled green/yellow (superimposed red plus green) fluorescence. Original magnification ×600.

FIG. 3. Illustrates vanadocenes induce apoptosis in human testicular cancer cells. [Left panels] FACS analysis: Two-color flow cytometric contour plots of Tera-2 cells treated with and without vanadocenes. Cells were incubated for 24 h in either control medium (0.1% DMSO) (A), or in medium supplemented with 100 μM VDA (C), VDCN (E), VDOCN (G), or VDCO (I) in 0.1% DMSO, fixed, permeabilized, and visualized for DNA-fragmentation in a TUNEL assay using TdT and FITC-dUTP. Red fluorescence represents nuclei counterstained with propidium iodide. Percentages indicate cells with increased dUTP incorporation. [Rightpanels] Confocal images: Two-color confocal laser scanning microscopy images of control and apoptotic cells. (B) Control cells visualized for dUTP incorporation using FITC-dUTP. Apoptotic nuclei of cells treated with VDA (D), VDCN (F), VDOCN (H) and VDCO (J) are recognized by fluorescein labeled green/yellow (superimposed red plus green) fluorescence. Original magnification ×600 are recognized by fluorescein labeled (green or yellow[i.e., superimposed red plus green] color) nuclei and apoptotic bodies within the nuclei. (original magnification ×600).

FIG. 4. Illustrates the formation of hyperdiploid nuclei and induction of apoptosis in vanadocene-treated Tera-2 testicular cancer cells. Cells were treated with vehicle, 12.5, 25, or 50 μM venadocene for 24 h, stained with propidium iodide and analysed by flow cytometry for DNA content. The percentages indicate the hyperdiploid/apoptotic nuclei.

FIG. 5. Illustrates Cytotoxic activity of metallocene dichlorides (A) and vanadocene on human glioblastoma cells. U373 glioblastoma cells were incubated with increasing concentrations of 5 metallocene dichlorides VDC, TDC, ZDC, HDC, and MDCT or 7 representative vanadocene VDC, VDSeCN, VDI, VDA, VDCN, VDH, and VDB for 24 hr in 96-well plates and the cell survival was determined by the MTT assay as described in materials and methods. Activity is expressed relative to DMSO controls. The data points represent the mean (±SD) value of three independent experiments.

FIG. 6. Illustrates the cytotoxic activity of VDSeCN in 4 human cancer cell lines. Fluorescence-activated cell sorter-correlated two parameter display (fluorescence from propidium iodide [PI], and fluorescence from MC540 staining) of AML (HL-60), breast cancer (MDA-MB-231 and BT-20) and brain tumor (U87) cells stained with MC540 and PI 24 h after treatment with vehicle (CON), 10, 50, or 100 μM of VDSeCN. The percentages indicate the fraction of cells at an early stage of apoptosis, as measured by single MC540 fluorescence, and the fraction of cells at an advanced stage apoptosis, as measured by dual MC540/PI fluorescence.

FIG. 7. Illustrates the formation of hyperdiploid nuclei and induction of apoptosis in vanadocene-treated AML HL-60 cells. Cells were treated with vehicle (Con 1 and Con 2), 10, 50 and 100 μM VDC or VDSeCN for 24 h, stained with propidium iodide and analysed by flow cytometry for DNA content. The percentages indicate the hyperdiploid/apoptotic nuclei.

FIG. 8. Illustrates the morphological features of breast cancer BT-20 cells treated with VDC. cells were incubated with vehicle (A), or 25 μM of VDC for 48 hr (B) or 72 hr (C) 24 hr and processed for immunofluorescence using a monoclonal antibody to α-tubulin (green fluorescence). VDC-treated cells showed marked shrinkage with disruption of microtubules and lost their ability to adhere to the substratum. Blue fluorescence represents nuclei stained with TOTO-3.

DETAILED DESCRIPTION

Vanadium is a physiologically essential element that can be found in both anionic and cationic forms with oxidation states ranging from −3 to +5 (I-V). This versatility provides unique properties to vanadium complexes. In particular, the catonic form of vanadium complexes with oxidation state +4 (IV) have been shown to function as modulators of cellular redox potential, regulate enzymatic phosphorylation, and exert pleiotropic effects in multiple biological systems by catalyzing the generation of reactive oxygen species (ROS). Besides the ability of vanadium metal to assume various oxidation states, its coordination chemistry also plays a key role in its interactions with various biomolecules. In particular, organometallic complexes of vanadium (IV) linked to bis (cycopentadienyl) moieties or vanadocene derivatives exhibit antitumor properties both in vitro and in vivo primarily via oxidative damage.

The following definitions are used, unless otherwise described: halo is fluoro, chloro, bromo, or iodo. Alkyl, alkoxy, etc. denote both straight and branched groups; but reference to an individual radical such as “propyl” embraces only the straight chain radical, a branched chain isomer such as “isopropyl” being specifically referred to.

It will be appreciated by those skilled in the art that compounds of the invention having a chiral center may exist in and be isolated in optically active and racemic forms. Some compounds may exhibit polymorphism. It is to be understood that the present invention encompasses any racemic, optically-active, polymorphic, or stereoisomeric form, or mixtures thereof, of a compound of the invention, which possess the useful properties described herein, it being well known in the art how to prepare optically active forms (for example, by resolution of the racemic form by recrystallization techniques, by synthesis from optically-active starting materials, by chiral synthesis, or by chromatographic separation using a chiral stationary phase) and how to determine antitumor activity using the standard tests described herein, or using other similar tests which are well known in the art.

Specific values listed below for radicals, substituents, and ranges, are for illustration only; they do not exclude other defined values or other values within defined ranges for the radicals and substituents.

Specifically, (C₁-C₆)alkyl can be methyl, ethyl, propyl, isopropyl, butyl, iso-butyl, sec-butyl, pentyl, 3-pentyl, or hexyl; (C₁-C₃)alkyl can be methyl, ethyl or propyl; halo(C1-C3)alkyl can be iodomethyl, bromomethyl, chloromethyl, fluoromethyl, trifluoromethyl, 2-chloroethyl, 2-fluoroethyl, 2,2,2-trifluoroethyl, or pentafluoroethyl; (C1-C3)alkoxy can be methoxy, ethoxy, or propoxy; and (C₂-C₆)alkanoyloxy can be acetoxy, propanoyloxy, butanoyloxy, isobutanoyloxy, pentanoyloxy, or hexanoyloxy.

As used herein, the following definitions define the stated terms:

“Organometallic compound” is an organic compound comprised of a metal attached directly to carbon (R-M).

“Coordination compound” is a compound formed by the union of a central metal atom or ion with ions or molecules called ligands or complexing agents.

“Ligand” or a “complexing agent” is a molecule, ion or atom that is attached to the central metal atom or ion of a coordination compound.

“Monodentate ligand” is a ligand having a single donor atom coordinated to the central metal atom or ion.

“Bidentate ligand” is a ligand having two donor atoms coordinated to the same central metal atom or ion.

“Oxovandium (IV) complex” is a coordination compound including vanadium as the central metal atom or ion, and the vanadium has an oxidation state of +4 (IV), and is double bonded to oxygen.

The present invention concerns organometallic vanadium complexes, and the finding that such oxovanadium complexes have potent and selective antitumor activity, and are particularly active and stable antitumor agents.

Compounds of the invention include oxovanadium (IV) containing organometallic complexes having antitumor activity. Preferred the oxovanadium (IV) complexes include at least one bidentate ligand. Suitable bidentate ligands include N, N; N, O; and O, O bidentate ligands. Examples of suitable bidentate ligands include bipyridyl, bridged bipyridyl, and acetophenone. Particularly, preferred oxovanadium compounds of the invention are those having the formulas II, III, IV, VI and VIII shown and described below.

Specifically, the vanadium (IV) compound is a compound of formula I:

wherein,

R₁-R₂ are each independently halo, OH₂, O₃SCF₃, N₃, CN, OCN, SCN or SeCN;

R₃-R₄ are each independently a cyclopentadienyl ring, wherein each cyclopentadienyl ring is optionally substituted with one or more (C1-C3)alkyl.

Specifically, halo is chloro, bromo, or iodo.

Specifically, (C1-C3)alkyl is methyl.

Specifically, the compound of formula I is VCp₂Cl₂, VCp₂Br₂, VCp₂I₂, VCp₂X₂, VCp₂(N₃)₂, VCp₂(CN)₂, VCp₂(NCO)₂, VCp₂(NCO)Cl, VCp₂(NCS)₂. 0.5H₂O, VCp₂(NCSe)₂, VCp₂Cl (CH₃CN)(FeCl₄), VCp₂(O₃SCF₃)₂, V(MeCP)₂Cl₂. 0.5 H₂O, V(Me₅Cp)₂Cl₂, VCp₂(acac), VCp₂(hf-acac), VCp₂(bpy), VCp₂(cat), VCp₂(dtc), VCp₂PH, or VCp₂H.

Specifically, the vanadium (IV) compound is a compound of formula II:

wherein

R and R¹ are each independently H, (C1-C3)alkyl, halogen, (C1-C3)alkoxy, halo(C1-C3)alkyl, cyano, (C₂-C₆)alkanoyloxy or nitro;

X and X¹ are each independently monodentate or bidentate ligands, or no ligand is present on X¹;

Y is a monodentate ligand; and

Specifically, X and X¹ are each independently OH₂, a bidentate ligand, or a monodentate ligand; wherein each ligand is optionally substituted with one or more (C1-C3)alkyl.

Specifically, (C1-C3)alkyl is methyl.

Specifically, R and R¹ are each independently H or (C1-C3)alkyl.

Specifically, the compound of fomula II is [VO(Bpy)(H₂O)₂](SO₄), [VO(SO₄)(Bpy)₂], [VO(Me₂-bpy)(H₂O)₂](SO₄), or [VO(SO₄)(Me₂-bpy)₂].

Specifically, the vanadium (IV) compound is a compound of formula III:

wherein

R² and R³ are each independently H, (C1-C3)alkyl, halogen, (C1-C3)alkoxy, halo(C1-C3)alkyl, cyano, (C₂-C₆)alkanoyloxy or nitro;

X² and X³ are each independently monodentate or bidentate ligands, or no ligand is present on X³;

Z is selected from O, CH₂, CH₂—CH₂ and CH═CH; and

Specifically, Z is CH═CH.

Specifically, Y is OH₂ or OSO₃.

Specifically, X² is OH₂, a bidentate ligand, or a monodentate ligand.

Specifically, X³ is a bidentate ligand or a monodentate ligand.

Specifically, R² and R³ are each independently H, (C1-C3)alkyl, halo, or nitro.

Specifically, (C1-C3)alkyl is methyl.

Specifically, halo is chloro.

Specifically, the compound of formula III is [VO(Bpy)(H₂O)₂](SO₄), [VO(SO₄)(Bpy)₂], [VO(Me₂-bpy)(H₂O)₂](SO₄), [VO(SO₄)(Me₂-bpy)₂], [VO(Phen)(H₂O)₂](SO₄), [VO(SO₄)(Phen)₂], [VO(Me₂-Phen)(H₂O)₂](SO₄), or [VO(SO₄)(Me₂-Phen)₂].

Specifically, the vanadium (IV) compound is a compound of formula IV:

wherein

R⁴, R⁵ and R⁶ are each independently H, (C1-C3)alkyl, halogen, (C1-C3)alkoxy, halo(C1-C3)alkyl, cyano, (C₂-C₆)alkanoyloxy or nitro;

X⁴ and X⁵ are each independently a monodentate or bidentate ligand, or no ligand is present on X⁵;

Y is a monodentate ligand; and

Specifically, R⁴-R⁶ are each independently H, (C1-C3)alkyl, halo or nitro.

Specifically, (C1-C3)alkyl is methyl.

Specifically, halo is chloro.

Specifically, Y is OH₂ or OSO₃.

Specifically, X⁵ is OH₂, a bidentate ligand, or a monodentate ligand.

Specifically, the compound of formula IV is [VO(Bpy)(H₂O)₂](SO₄), [VO(S₄)(BPY)₂], [VO(Me₂-bpy)(H₂O)₂](SO₄), [VO(SO₄)(Me₂-bpy)₂], [VO(Phen)(H₂O)₂](SO₄), [VO(SO₄)(Phen)₂], [VO(Me₂-Phen)(H₂O)₂](SO₄), [VO(SO₄)(Me₂-Phen)₂], [VO(Cl-Phen)(H₂O)₂](SO₄), [VO(SO₄)(Cl-Phen)₂], [VO(NO₂-Phen)(H₂O)₂](SO₄), or [VO(SO₄)(NO₂-Phen)₂].

Specifically, the cancer is testicular cancer, Hodgkin's lymphoma, multiple myeloma, or non-Hodgkin's lymphoma.

Another specific method of the invention comprises administering an oxovanadium compound.

Another specific method of the invention comprises administering a vanadocene compound with the proviso that the vanadocene compound is not VCp₂Cl₂.

The invention provides novel compounds. Accordingly, there is provided a compound of formula II:

wherein

R and R¹ are each independently H, (C1-C3)alkyl, halogen, (C1-C3)alkoxy, halo(C1-C3)alkyl, cyano, (C₂-C₆)alkanoyloxy or nitro;

X and X¹ are each independently a monodentate or bidentate ligand, or no ligand is present on X¹; and

Y is a monodentate ligand;

or a pharmaceutically acceptable salt thereof;

with the proviso that the compound is not [VO(SO₄)(Bpy)₂].

Specifically, X and X¹ are each independently OH₂, a bidentate ligand, or a monodentate ligand; wherein each ligand is optionally substituted with one or more (C1-C3)alkyl.

Specifically, (C1-C3)alkyl is methyl.

Specifically, R and R¹ are each independently H or (C1-C3)alkyl.

Specifically, the compound of fomula II is [VO(Bpy)(H₂O)₂](SO₄), [VO(SO₄)(Bpy)₂], [VO(Me₂-bpy)(H₂O)₂](SO₄), or [VO(SO₄)(Me₂-bpy)₂]

Another specific compound of the present invention is a compound of formula III:

wherein

R² and R³ are each independently H, (C1-C3)alkyl, halogen, (C1-C3)alkoxy, halo(C1-C3)alkyl, cyano, (C₂-C₆)alkanoyloxy or nitro;

X² and X³ are each independently a monodentate or bidentate ligand, or no ligand is present on X³; and

Z is O, CH₂, CH₂—CH₂ or CH═CH;

or a pharmaceutically acceptable salt thereof;

with the proviso that the compound is not [VO(Phen)(H₂O)₂](SO₄) or [VO(SO₄)(Phen)₂].

Specifically, Z is CH═CH.

Specifically, Y is OH₂ or OSO₃.

Specifically, X² is OH₂, a bidentate ligand, or a monodentate ligand.

Specifically, X³ is a bidentate ligand or a monodentate ligand.

Specifically, R² and R³ are each independently H, (C1-C3)alkyl, halo, or nitro.

Specifically, (C1-C3)alkyl is methyl.

Specifically, halo is chloro.

Specifically, the compound of formula III is [VO(Bpy)(H₂O)₂](SO₄), [VO(SO₄)(Bpy)₂], [VO(Me₂-bpy)(H₂O)₂](SO₄), [VO(SO₄)(Me₂-bpy)₂], [VO(Phen)(H₂O)₂](SO₄), [VO(SO₄)(Phen)₂], [VO(Me₂-Phen)(H₂O)₂](SO₄), or [VO(SO₄)(Me₂-Phen)₂].

Another specific compound of the present invention is a compound of formula IV:

wherein

R⁴, R⁵ and R⁶ are each independently H, (C1-C3)alkyl, halogen, (C1-C3)alkoxy, halo(C1-C3)alkyl, cyano, (C₂-C₆)alkanoyloxy or nitro;

X⁴ and X⁵ are each independently a monodentate or bidentate ligand; and

Y is a monodentate ligand

or a pharmaceutically acceptable salt thereof;

with the proviso that the compound is not [VO(Phen)(H₂O)₂](SO₄) or [VO(SO₄)(Phen)₂].

Specifically, R⁴-R⁶ are each independently H, (C1-C3)alkyl, halo or nitro.

Specifically, (C1-C3)alkyl is methyl.

Specifically, halo is chloro.

Specifically, Y is OH₂ or OSO₃.

Specifically, X⁵ is OH₂, a bidentate ligand, or a monodentate ligand.

Specifically, the compound of formula IV is [VO(Bpy)(H₂O)₂](SO₄), [VO(SO₄)(BPY)₂], [VO(Me₂-bpy)(H₂O)₂](SO₄), [VO(SO₄)(Me₂-bpy)₂], [VO(Phen)(H₂O)₂](SO₄), [VO(SO₄)(Phen)₂], [VO(Me₂-Phen)(H₂O)₂](SO₄), [VO(SO₄)(Me₂-Phen)₂], [VO(Cl-Phen)(H₂O)₂](SO₄), [VO(SO₄)(Cl-Phen)₂], [VO(NO₂-Phen)(H₂O)₂](SO₄), or [VO(SO₄)(NO₂-Phen)₂].

Another specific compound of the present invention is a compound of formula V:

wherein

R⁷ and R⁹ are each independently H, (C1-C3)alkyl, (C1-C3)alkoxy, or halo(C₁-C3)alkyl;

R⁸ is H, (C1-C3)alkyl, halo, (C1-C3)alkoxy, or halo(C1-C3)alkyl;

Y and Y¹ are each independently a monodentate or bidentate ligand; and

n is 0 or 1;

or a pharmaceutically acceptable salt thereof.

Another specific compound of the present invention is a compound of formula VII:

wherein

R¹ and R² are each independently a cyclopentadienyl ring, wherein any cyclopentadienyl ring may optionally be substituted with one or more (C₁-C6)alkyl; and

R¹⁰-R¹³ are each independently H, halo, or (C1-C6)alkyl; or a pharmaceutically acceptable salt thereof.

Specifically, R¹ and R² are each a cyclopentadienyl ring.

Specifically, R¹⁰-R¹³ are each H.

Specifically, the compound of formula VII is the compound CP₂V(O₂C₆H₄).

A specific pharmaceutical composition of the present invention comprises a compound of formula II:

wherein

R and R¹ are each independently H, (C1-C3)alkyl, halogen, (C1-C3)alkoxy, halo(C1-C3)alkyl, cyano, (C₂—C₆)alkanoyloxy or nitro;

X and are each independently a monodentate or bidentate ligand, or no ligand is present on X¹; and

Y is a monodentate ligand;

or a pharmaceutically acceptable salt thereof;

and a pharmaceutically acceptable carrier.

Specifically, X and X¹ are each independently OH₂, a bidentate ligand, or a monodentate ligand, wherein each ligand is optionally substituted with one or more (C1-C3)alkyl.

Specifically, (C1-C3)alkyl is methyl.

Specifically, R and R¹ are each independently H or (C1-C3)alkyl.

Specifically, the compound of fomula II is [VO(Bpy)(H₂O)₂](SO₄), [VO(SO₄)(Bpy)₂], [VO(Me₂-bpy)(H₂O)₂](SO₄), or [VO(SO₄)(Me₂-bpy)₂].

Another specific pharmaceutical composition of the present invention comprises a compound of formula III:

wherein

R² and R³ are each independently H, (C1-C3)alkyl, halogen, (C1-C3)alkoxy, halo(C1-C3)alkyl, cyano, (C₂-C₆)alkanoyloxy or nitro;

X² and X³ are each independently a monodentate or bidentate ligand, or no ligand is present on X³; and

Z is O, CH₂, CH₂—CH₂ or CH═CH;

or a pharmaceutically acceptable salt thereof;

and a pharmaceutically acceptable carrier;

with the proviso that the compound is not [VO(Phen)(H₂O)₂](SO₄).

Specifically, Z is CH═CH.

Specifically, Y is OH₂ or OSO₃.

Specifically, X² is OH₂, a bidentate ligand, or a monodentate ligand.

Specifically, X³ is a bidentate ligand or a monodentate ligand.

Specifically, R² and R³ are each independently H, (C1-C3)alkyl, halo, or nitro.

Specifically, (C1-C3)alkyl is methyl.

Specifically, halo is chloro.

Specifically, the compound of formula III is [VO(Bpy)(H₂O)₂](SO₄), [VO(SO₄)(BPY)₂], [VO(Me₂-bpy)(H₂O)₂](SO₄), [VO(SO₄)(Me₂-bpy)₂], [VO(Phen)(H₂O)₂](SO₄), [VO(SO₄)(Phen)₂], [VO(Me₂-Phen)(H₂O)₂](SO₄), or [VO(SO₄)(Me₂-Phen)₂].

Another pharmaceutical composition of the present invention comprises a compound of formula IV:

wherein

R⁴, R⁵ and R⁶ are each independently H, (C1-C3)alkyl, halogen, (C1-C3)alkoxy, halo(C1-C3)alkyl, cyano, (C₂-C₆)alkanoyloxy or nitro;

X⁴ and X⁵ are each independently a monodentate or bidentate ligand; and

Y is a monodentate ligand;

or a pharmaceutically acceptable salt thereof;

and a pharmaceutically acceptable carrier;

with the proviso that the compound is not [VO(Phen)(H₂O)₂](SO₄).

Specifically, R⁴-R⁶ are each independently H, (C1-C3)alkyl, halo or nitro.

Specifically, (C1-C3)alkyl is methyl.

Specifically, halo is chloro.

Specifically, Y is OH₂ or OSO₃.

Specifically, X⁵ is OH₂, a bidentate ligand, or a monodentate ligand.

Specifically, the compound of formula IV is [VO(Bpy)(H₂O)₂](SO₄), [VO(SO₄)(Bpy)₂], [VO(Me₂-bpy)(H₂O)₂](SO₄), [VO(SO₄)(Me₂-bpy)₂], [VO(Phen)(H₂O)₂](SO₄), [VO(SO₄)(Phen)₂], [VO(Me₂-Phen)(H₂O)₂](SO₄), [VO(SO₄)(Me₂-Phen)₂], [VO(Cl-Phen)(H₂O)₂](SO₄), [VO(SO₄)(Cl-Phen)₂], [VO(NO₂-Phen)(H₂O)₂](SO₄), or [VO(SO₄)(NO₂-Phen)₂].

Administration of the compounds as salts may be appropriate. Examples of acceptable salts include alkali metal (for example, sodium, potassium or lithium) or alkaline earth metal (for example calcium) salts, however, any salt that is non-toxic and effective when administered to the animal being treated is acceptable.

Acceptable salts may be obtained using standard procedures well known in the art, for example by reacting a sufficiently acidic compound with a suitable base affording a physiologically acceptable anion.

The compositions of the invention can be formulated as pharmaceutical compositions and administered to an animal host, such as a human patient in a variety of forms adapted to the chosen route of administration, i.e., orally or parenterally, by intravenous, intramuscular, topical or subcutaneous routes.

Thus, the present compounds may be systemically administered, e.g., orally, in combination with a pharmaceutically acceptable vehicle such as an inert diluent or an assimilable edible carrier. They may be enclosed in hard or soft shell gelatin capsules, may be compressed into tablets, or may be incorporated directly with the food of the patient's diet. For oral therapeutic administration, the active compound may be combined with one or more excipients and used in the form of ingestible tablets, buccal tablets, troches, capsules, elixirs, suspensions, syrups, wafers, and the like. Such compositions and preparations should contain at least 0.1% of active compound. The percentage of the compositions and preparations may, of course, be varied and may conveniently be between about 2 to about 60% of the weight of a given unit dosage form. The amount of active compound in such therapeutically useful compositions is such that an effective dosage level will be obtained. When administered orally, the compositions of the invention can preferably be administered in a gelatin capsule.

The tablets, troches, pills, capsules, and the like may also contain the following: binders such as gum tragacanth, acacia, corn starch or gelatin; excipients such as dicalcium phosphate; a disintegrating agent such as corn starch, potato starch, alginic acid and the like; a lubricant such as magnesium stearate; and a sweetening agent such as sucrose, fructose, lactose or aspartame or a flavoring agent such as peppermint, oil of wintergreen, or cherry flavoring may be added. When the unit dosage form is a capsule, it may contain, in addition to materials of the above type, a liquid carrier, such as a vegetable oil or a polyethylene glycol. Various other materials may be present as coatings or to otherwise modify the physical form of the solid unit dosage form. For instance, tablets, pills, or capsules may be coated with gelatin, wax, shellac or sugar and the like. A syrup or elixir may contain the active compound, sucrose or fructose as a sweetening agent, methyl and propylparabens as preservatives, a dye and flavoring such as cherry or orange flavor. Of course, any material used in preparing any unit dosage form should be pharmaceutically acceptable and substantially non-toxic in the amounts employed. In addition, the active compound may be incorporated into sustained-release preparations and devices.

The compositions of the invention may also be administered intravenously or intraperitoneally by infusion or injection. Solutions of the active composition can be prepared in water, optionally mixed with a nontoxic surfactant. Dispersions can also be prepared in glycerol, liquid polyethylene glycols, triacetin, and mixtures thereof and in oils. Under ordinary conditions of storage and use, these preparations contain a preservative to prevent the growth of microorganisms.

The pharmaceutical dosage forms suitable for injection or infusion can include sterile aqueous solutions or dispersions or sterile powders comprising the active ingredient which are adapted for the extemporaneous preparation of sterile injectable or infusible solutions or dispersions, optionally encapsulated in liposomes. In all cases, the ultimate dosage form should be sterile, fluid and stable under the conditions of manufacture and storage. The liquid carrier or vehicle can be a solvent or liquid dispersion medium comprising, for example, water, ethanol, a polyol (for example, glycerol, propylene glycol, liquid polyethylene glycols, and the like), vegetable oils, nontoxic glyceryl esters, and suitable mixtures thereof. The proper fluidity can be maintained, for example, by the formation of liposomes, by the maintenance of the required particle size in the case of dispersions or by the use of surfactants. The prevention of the action of microorganisms can be brought about by various antibacterial and antifungal agents, for example, parabens, chlorobutanol, phenol, sorbic acid, thimerosal, and the like. In many cases, it will be preferable to include isotonic agents, for example, sugars, buffers or sodium chloride. Prolonged absorption of the injectable compositions can be brought about by the use in the compositions of agents delaying absorption, for example, aluminum monostearate and gelatin.

Sterile injectable solutions are prepared by incorporating the active composition in the required amount in the appropriate solvent with various of the other ingredients enumerated above, as required, followed by filter sterilization. In the case of sterile powders for the preparation of sterile injectable solutions, the preferred methods of preparation are vacuum drying and the freeze drying techniques, which yield a powder of the active ingredient plus any additional desired ingredient present in the previously sterile-filtered solutions.

For topical administration, the present compositions may be applied in pure form, i.e., when they are liquids. However, it will generally be desirable to administer them to the skin as compositions or formulations, in combination with a dermatologically acceptable carrier, which may be a solid or a liquid.

Useful solid carriers include finely divided solids such as talc, clay, microcrystalline cellulose, silica, alumina and the like. Useful liquid carriers include water, alcohols or glycols or water-alcohol/glycol blends, in which the present compounds can be dissolved or dispersed at effective levels, optionally with the aid of non-toxic surfactants. Adjuvants such as fragrances and additional antimicrobial agents can be added to optimize the properties for a given use. The resultant liquid compositions can be applied from absorbent pads, used to impregnate bandages and other dressings, or sprayed onto the affected area using pump-type or aerosol sprayers.

Thickeners such as synthetic polymers, fatty acids, fatty acid salts and esters, fatty alcohols, modified celluloses or modified mineral materials can also be employed with liquid carriers to form spreadable pastes, gels, ointments, soaps, and the like, for application directly to the skin of the user.

Examples of useful dermatological compositions which can be used to deliver the compounds of formula I to the skin are known to the art; for example, see Jacquet et al. (U.S. Pat. No. 4,608,392), Geria (U.S. Pat. No. 4,992,478), Smith et al. (U.S. Pat. No. 4,559,157) and Wortzman (U.S. Pat. No. 4,820,508).

Useful dosages of the compounds of the present invention can be determined by comparing their in vitro activity, and in vivo activity in animal models. Methods for the extrapolation of effective dosages in mice, and other animals, to humans are known to the art; for example, see U.S. Pat. No. 4,938,949.

Generally, the concentration of the compositions of the invention in a liquid composition, such as a lotion, will be from about 0.1-50 wt-%, preferably from about 0.5-5 wt %. The concentration in a semi-solid or solid composition such as a gel or a powder will be about 0.1-5 wt-%, preferably about 0.5-2.5 wt-%.

The amount of the composition required for use in treatment will vary not only with the particular salt selected but also with the route of administration, the nature of the condition being treated and the age and condition of the patient and will be ultimately at the discretion of the attendant physician or clinician.

In general, however, a suitable dose will be in the range of from about 0.1 to about 150 mg/kg, e.g., from about 10 to about 75 mg/kg of body weight per day, such as 3 to about 50 mg per kilogram body weight of the recipient per day, preferably in the range of 1 to 100 mg/kg/day, most preferably in the range of 5 to 20 mg/kg/day.

The compositions are conveniently administered in unit dosage form; for example, containing 5 to 1000 mg, conveniently 10 to 750 mg, most conveniently, 50 to 500 mg of active ingredient per unit dosage form.

Ideally, the active ingredient should be administered to achieve peak plasma concentrations of the active compound of from about 0.5 to about 75 μM, preferably, about 1 to 50 μM, most preferably, about 2 to about 30 μM. This may be achieved, for example, by the intravenous injection of a 0.05 to 5% solution of the active ingredient, optionally in saline, or orally administered as a bolus containing about 1-100 mg of the active ingredient. Desirable blood levels may be maintained by continuous infusion to provide about 0.01-5.0 mg/kg/hr or by intermittent infusions containing about 0.4-15 mg/kg of the active ingredient(s).

The desired dose may conveniently be presented in a single dose or as divided doses administered at appropriate intervals, for example, as two, three, four or more sub-doses per day. The sub-dose itself may be further divided, e.g., into a number of discrete loosely spaced administrations; such as multiple inhalations from an insufflator or by application of a plurality of drops into the eye.

The compositions of the invention are useful for prevention and of cancer.

Following i.m. administration, the compositions of the invention enter the blood stream within about 10-15 minutes and reach a maximum concentration in the blood within one hour of administration, at which point they can be found throughout the circulatory related organs.

The antitumor activity of the compositions of the invention can be determined using assays that are known in the art, or can be determined using assays similar to those described in the following examples.

EXAMPLES

Abbreviations.

Cp⁻, cyclopentadienyl anion; acac, acetonylacetonate; Bpy, 2,2′ Bipyridine; Hfacac, hexafluor0acetylacetonate; Cat, catecholate; Dtc, diethyl dithio carbamate; PH, N-phenyl bezohydroxamic acids; H, acethydroxamic acid; OTf, trifluorometahne sulphonate; THF, tetrahydrofuran; DMSO, dimethyl sulfoxide; CH₃CN, acetonitrile; CH₂Cl₂, dichloromethane; d-d, laportte spin forbidden transitions; LMCT, ligand to metal charge transfer transitions; p-p*, intraligand charge transfer transitions; s, m, w: strong, medium, and weak; b, broad; v, very; sh, shoulder.

Materials and Methods

Reagents used were reagent grade, unless otherwise stated. All solvents were used as received from Aldrich Sure Seal bottle, <0.005% water. Tetrahydrofuran was dried by distillation over solid sodium. Dichloromethane (reagent grade) was purified as follows: stirred overnight with concentrated sulfuric acids, seperated, washed with saturated aqueous NaHCO₃, washed with aqueous KOH/KCl, washed with distilled water, dried over anhydrous MgSO₄, and distilled from KOH. Perrin, D. D., Armereago, W. L. F. In Purification of Laboratory Chemicals, 3rd.ed.; pergamon press: New York, 1988. Sodium thiophenolate was prepared by the reaction of a stoichiometric amount of NaOMe with thiophenol in methanol. The precipitated solid was washed with cold methanol and dried under high vacuum. All the solvents were deoxygeneted by purging with argon, and reactions were carried out under an argon atmosphere by using standard Schlenk techniques.

The infra-red spectral data were recorded on a FT-Nicolet model Protege 460. The solid samples were taken in a KBr pellet and the frequencies were generally in the range of 4000-500 cm⁻¹. UV-vis spectra were recorded in a quartz cell or cuvette on Beckman model DU 7400 spectrophotometer and the spectral band are registered between 250-800 nm range. NMR spectra were recorded in CDCl₃ or Me₂SO-d⁶ on a Varian (300 Mhz) NMR spectrometer. Chemical shifts are reported as δ values downfield from an internal standard of Me₄Si. Melting points were determined with Melt-temp laboratory devices Inc. apparatus, attached to Fluke 51 K/J Thermometer.

All elemental analysis were performed by Atlantic Microlab, Inc., Norcross, Ga., and the analytical results are supplied as supporting information unless otherwise stated all operations were carried out at room temperature.

Example I Vanadocene Compounds

Chemical Synthesis

All the metal tetrachlorides, MCl₄ (M=Ti, V, Mo, Hf, & Zr) were purchased from Aldrich Chemical Co. (Milwaukee, Wis.).

Compounds 1-25 are shown in Synthetic Schemes 1-4 and Tables 1-4. VCp₂Cl₂, TiCp₂Cl₂, ZrCP₂Cl₂, and MoCp₂Cl₂ were prepared by known procedures. Wilkinson, G., Birmingham, J. M. Bis-cyclopentadienyl compounds of Ti, Zr, V, Nb, and Ta. J. Am. Chem. Soc., 76: 4281-4284, 1954. Cardin, D. J., Lappart, M. F., Raston, C. L., Riley, P. I. In Comprehensive organometallic chemistry; Wilkinson, G. ed. New York: Pergamon; 3: 554-646, 1982. Eisch, J. J., King, R. B. Organometallic synthesis, Academic press, New York,N.Y. Vol. 1, 75-76, 1965. The purity was checked by ¹HNMR and IR spectroscopy and by elemental analysis. The HfCp₂Cl₂ was directly purchased from aldrich Chemical Co. The complex VCp₂Cl₂ was purified by anaerobic Soxhlet extraction with CH₂Cl₂ at 44° C. (under partial vacuum). TiCp₂Cl₂ was recrystallized from THF.

Compounds 1-5 may be prepared as shown in Synthetic Scheme 1; compounds 6-15 may be prepared as shown in Synthetic Scheme 2; compounds 16-22 may be prepared as shown in Synthetic Scheme 3; and compounds 23-25 may be prepared as shown in Synthetic Scheme 4 (below).

HfCp₂Cl₂, (Compound 1). Yield: 75%. M.P. 330-335° C. Anal. Calcd. for HfC₁₀H₁₀Cl₂: C, 31.62, H, 2.63; Cl, 18.71. Found: C, 32.09; H, 2.75; Cl, 18.98. UV-vis: (CH₂Cl₂) λ_(max): 312(LMCT), 268, 232 (π-π*) nm. IR (KBr Disc): 3105(vs), 1365(m), 1126(m), 1014(vs), 920(s,d), 802(vs), 816(vs), 611(m) cm⁻¹. ¹HNMR (δppm, CDCl₃): 6.37 (s, 10H, 2×C₅H₅).

MOCp₂Cl₂, (Compound 2). Yield: 37%. M.P. 220° C. Anal. Calcd. for MoC₁₀H₁₀Cl₂: C, 40.4, H, 3.37; Cl, 23.9. Found: C, 40.8; H, 3.39; Cl, 24.4. UV-vis: (DMSO) λmax: 678, 436 (d-d), 299(LMCT), 283, 267 (π-π*) nm. IR (KBr Disc): 3093(vs), 1420(vs), 1375(m), 1100(m), 1060(m), 825(vs,d), 590(m) cm⁻¹. ¹HNMR (δppm, DMSO-d⁶): 6.27 (s, 10H, 2×C ₅H₅).

TiCp₂Cl₂, (Compound 3). Yield: 45%. M.P. 290° C. (decomposes). Anal. Calcd. for TiC₁₀H₁₀Cl₂: C, 48.2, H, 4.01; Cl, 28.5. Found: C, 48.56; H, 4.03; Cl, 28.78. UV-vis: (CH₂Cl₂) λ_(max): 526, 391 (LMCT), 314, 255 (π-π*) nm. IR (KBr Disc): 3105(m), 1441(s), 1368(m), 1130(m), 1016(vs), 956(m), 872(s), 820(vs)) cm⁻¹. ¹HNMR (δ ppm, CDCl₃): 6.57 (s, 10H, 2×C₅H₅).

ZrCp₂Cl₂, (Compound 4). Yield: 78%. M.P. 240-245° C. (decomposes). Anal. Calcd. for ZrC₁₀H₁₀Cl₂: C, 41.09, H, 3.4; Cl, 24.31. Found: C, 41.01; H, 3.4; Cl, 24.84. UV-vis: (CH₂Cl₂) λ_(max): 341 (LMCT), 294, 236 (π-π*) nm. IR (KBr Disc): 3104(m), 1435(s), 1363(m), 1122(m), 1014(vs), 815(s), 850(sb), 610(m)) cm⁻¹. ¹HNMR (δ ppm, CDCl₃): 6.46 (s, 10H, 2×C₅H₅).

VCp₂Cl₂, (Compound 5). Yield: 55%. M.P. 248-255° C. (decomposes). Anal. Calcd. for VC₁₀H₁₀Cl₂: C, 47.62, H, 3.97; Cl, 28.1. Found: C, 47.88; H, 4.04; Cl, 27.64. UV-vis: (CH₂Cl₂) λ_(max): 776, 647 (d-d), 380 (LMCT), 283, 244 (π-π) nm. IR (KBr Disc): 3095(s), 1444(s), 1433(s), 1368(m), 1363(m), 1130(m), 1070(m), 1010(m), 887(m), 825(vs) cm⁻¹.

VCp₂Br₂, (Compound 6). To a 20 ml acetone solution of VCp₂Cl₂ (0.2 g, 8 mmol) was added 0.7 g (80 mmol) of solid LiBr with stirring, and the reaction mixture was allowed to reflux for 4 h. The solvent was removed afterwards through vacuum and dried. The deep green product was extracted with 50 ml of boiling CHCl₃ and the solution was saturated with dry HBr gas before it was left overnight for crystallization at −20° C. The bright green crystals were collected on a frit and washed with hexane and diethyl ether. Yield: 90%. M.P. turns darker gradually over the range 250-350° C. (decomposes). Anal. Calcd. for VC₁₀H₁₀Br₂: C, 35.19, H, 2.29; Br, 46.92. Found: C, 35.19; H, 2.9; Br, 46.91. UV-vis: (CH₂Cl₂) λ_(max): 773, (d-d), 412 (LMCT), 298, 232 (π-π*) nm. IR (KBr Disc): 3089(vs), 1425(s), 1431(m), 1373(m), 1363(w), 1128(w), 1024(m), 1014(m), 887(m), 825(vs) cm⁻¹.

VCp₂I₂, (Compound 7). To anhydrous THF (25 mL) were added VCp₂Cl₂. (0.1 5 g, 6 mmol) and KI (0.99 g, 60 mmol). This reaction mixture was refluxed overnight under argon. The resulting dark red-brown solution was seperated from the inorganic salts by filtration and the solvent was evaporated under vacuum. The dark red materials were scratched out from the bottom of the container in the presence of dry hexane. The solvent was removed by cannula techniques with double edged needles under argon pressure. The solid was dried under vacuum and stored under argon. This compound is extremely sensitive to moisture and readily decomposes in halogenated solvents, but it is stable in DMSO. Yield: 55%. M.P.: Could not be measured; compound gets sticky during handling in air. Anal.Calcd.for VC₁₀H₁₀I₂: C, 27.58; H, 2.3; I, 58.4. Found: C, 28.1; H, 2.42; I, 58.9 UV-Vis:(CH₂Cl₂) λ_(max): 620, 552, (d-d), 352(LMCT), 296, 232,(π-π*) nm. IR (KBr Disc): 3300 (vb), 3095(s), 2950(s), 1712(w), 1574(w), 1425(s), 1431(m), 1373(m) 1363(w), 1182(m), 1128(w), 1024(m), 1014(m), 887(m), 825(vs) cm⁻¹.

VCp₂X₂. The pseudo-halide derivatives with X=N₃ ⁻(Compound 8), CN⁻ (Compound 9), OCN⁻ (Compound 10), and SCN⁻ (Compound 12) were prepared by following the procedure described in Doyle, G., Tobias, R. S. Pseudohalide and chelate complexes of bis(cyclopentadienyl)vanadium(IV). Inorg. Chem., 7: 2479-2484, 1968. The pure compounds were isolated either recrystallization or from Soxhlet extraction. The purity of these complexes were checked by elemental analysis, melting point data and UV-visible and IR spectrum. The results are given below:

VCp₂(N₃)₂, (Compound 8). Yield: 65%. M.P. Sublimes at 173° C. (decomposes). Anal. Calcd. for VC₁₀H₁₀N₆: C, 45.28, H, 3.77; N, 31.2. Found: C, 45.28; H, 3.73; N, 31.16. UV-vis: (CH₂Cl₂) λ_(max): 434 (d-d), 314 (LMCT), 257, 233 (π-π*)nm. IR (KBr Disc): 3125(m), 3111(m), 3104(m), 3079(m), 2067(vs), 2031(vs), 1448(m), 1375(m), 1330(m), 1280(m), 1126(w), 1080(w), 1024(m), 835(vs), 646(w), 590(m), 438(m), 400(w) cm⁻¹.

VCp₂(CN)₂, (Compound 9). Yield: 75%. M.P. Sublimes at 173° C. (decomposes). Anal. Calcd. for VC₁₂H₁₀N₂: C, 61.89, H, 4.29; N, 12.0. Found: C, 60.98; H, 4.30; N, 11.45. UV-vis: (CH₂Cl₂) λ_(max): 605 (d-d), 394 (LMCT), 307, 250 (π-π*) nm. IR (KBr Disc): 3450(m,b), 3114(vs), 2120(s), 2110(s), 1435(s), 1420(s), 1369(m), 1373(w), 1126(m), 1014(s), 881(s), 858(vs), 845 (vs), 480(m), 400(m) cm⁻¹.

VCp₂(NCO)₂, (Compound 10). Yield: 55%. M.P. 287° C. (decomposes). Anal. Calcd. for VC₁₂H₁₀N₂O₂: C, 54.3, H, 3.8; N, 10.6. Found: C, 53.85; H, 3.97; N, 10.2. UV-vis: (CH₂Cl₂) λ_(max): 742 (d-d), 373 (LMCT), 277, 237 (π-π*) nm. IR (KBr Disc): 3531(m), 3110(m), 2657(w), 2248(vs), 2117(vs), 2170(vs), 1330(s), 1024(w), 833(vs), 603(s), 593 (s), 420(m) cm⁻¹.

VCp₂(NCO)Cl, (Compound 11). The dark brown powder was isolated by following the procedure described for the Titanium analogue. Köpf-Maier, P., Grabowski, S., Köpf, H. Tumorhemmung durch Metallocene: Titan-Komplexe des type [TiCp₂XY] und [TiCpX₂Y]. Eur. J.Med.Chem-Chim. Ther. 19: 347-352, 1984. Anal. Calcd. for VC₁₁H₁₀NOCl: C, 51.06, H, 3.87; N, 5.41, Cl, 13.73. Found: C, 51.35; H, 3.97; N, 5.65, Cl, 13.45. UV-vis: (CH₂Cl₂) λ_(max): 710 (d-d), 490 (LMCT), 257, 227 (π-π*) nm. IR (KBr Disc): 3513(sp,w), 3110(m), 2657(w), 2117(vs), 1444(m), 1330(s), 1261(w), 1018(m), 950(m), 833(vs), 635(s), 424(w) cm⁻¹.

VCp₂(NCS)₂. 0.5H₂O, (Compound 12). Yield: 75%. M.P. The compound sublimes at 150° C. (decomposes). Anal. Calcd. for VC₁₂H₁₁N₂O_(1/2)S₂:C, 47.05, H, 3.59; N, 9.15, S, 20.91. Found: C, 47.55; H, 3.26; N, 9.06; S, 20.91. UV-vis: (CH₂Cl₂) λ_(max): 739 (d-d), 401 (LMCT), 463 (SCN⁻: π-π*), 251, 270 (π-π*) nm. IR (KBr Disc): 3400(w,b), 3087(s), 2086(vs), 2067(vs), 1433(s), 1423(m), 1010(m), 1070(m) 840(vs), 480(vw), 410(m) cm⁻¹.

VCp₂(NCSe)₂, (Compound 13). To a stirring solution of VCp₂Cl₂, (0.4g, 1.6 mmol) in anhydrous acetone (25 ml) under argon, was added solid KNCSe (0.85 g, 8 mmol). The reaction mixture was allowed to stir for 4 h at room temperature. The resulting red brown solution was subjected to rotatory vaporization and the pure microcrystalline red compound was isolated from the crude product through Soxhlet extraction using dichloromethane as solvent. Yield: 60%. M.P. The compound slowly turns black, decomposes at 250-275° C. (decomposes). Anal. Calcd. for VC₁₂H₁₀N₂Se₂: C, 36.83, H, 2.56; N, 7.1. Found: C, 36.85; H, 2.64; N, 6.97. UV-vis: (CH₂Cl₂) λ_(max): 716 (d-d), 456 (LMCT), 488 (SeCN⁻: π-π*), 251, 270 (π-π*) nm. IR (KBr Disc): 3475(m), 3076(s), 2085(vs), 2065(vs), 1444(m), 1431 (s), 1126(w), 1074(w), 1008 (m), 962 (m) 843(vs) cm⁻¹.

VCp₂Cl (CH₃CN)(FeCl₄), (Compound 14). Compound (14) was prepared by following the procedure described for the corresponding titanium complex. Neuse, E. W., Meirim, M. G. A chlorotitanocene tetrachlorferrate complex stabilized by acetonitrile coordination. Transition Met. Chem., 9: 337-338, 1984. In the instant synthesis, the 1:1.1 stoichiometric mole ratio between VCp₂Cl₂ and anhydrous FeCl₃ solution was strictly maintained in acetonitrile solution. The dark green precipitate was isolated from the reduced volume of the parent solution after overnight standing at −20° C. Yield: 90%. M.P. Not determined. Anal. Calcd. for: VC₁₂ H₁₃N Cl₅Fe: C, 31.6; H, 2.9; N, 3.1; Cl, 39.98. Found: yet to receive the data. UV-Vis : (CH₃ CN) λ_(max): 648, 575, (d-d), 362 (Superimposed bands of LMCT of Cp₂V²⁺ and FeCl₄ ⁻), 311 (FeCl₄ ⁻, LMCT), 265(sh), (π-π* of Cp rings), 240( superimposed bands of π-π* of Cp rings and FeCl₄ ⁻ nm. IR (KBr Disc): 3386(sb), 3109(m), 2924(m), 2360(w), 2318(s), 2289(m), 1622(m), 1447(s), 1435(m), 1358(w), 1128(m), 1027(s), 1012(s), 856(vs), 846(s) cm

VCp₂(O₃SCF₃)₂, (Compound 15). The generation of VCp₂(O₃SCF₃)₂ in THF solution was induced by following the procedure that was described for Titanium analogue. Thewalt, U., Berhalter, K. Kationische Komplexe Mit Der (η⁵—C₅H₅)₂Ti^(IV)-Baugruppe: Darstellung und Struktur Von [(η⁵—C₅H₅)₂ Ti(bpy)]²⁺ (CF₃SO₃)₂. J. Organometallic Chem., 302: 193-200, 1986. The precipitated silver chloride was removed by filtration and the filtrate evaporated to dryness. The solid green residue was redissolved in 20 mL of CH₂Cl₂, filtered again through cannula with one end covered with filter paper—cotton assembly, securely tightened by fine bore copper wire. The dark green precipitate was isolated from dichloromethane using diethyl ether as a cosolvent. The compound is moisture-sensitive.Yield: 40%, m.p. at 137° C. decomposition starts. Anal. Calcd.for VC₁₂H₁₀S₂O₆F₆: C, 30.06; H, 2.09; S, 13.36. Found: C, 29.98; H, 2.18; S, 13.19. UV-Vis: (DMSO) λ_(max): 620 (d-d), 379 (LMCT), 286, 261(π-π*) IR (KBr Disc): 3400(s,b), 3093(m), 1635(m), 1446(s), 1436(s), 1259(vb,d) 1178(vs), 1033(vs), 885(s), 822(vs),770(m), 643(vs,d), 580, (m), 518(vs)

VCp₂(acac)(O₃SCF₃), (Compound 16). Dark black colored large crystals were obtained by following the literature procedure. Doyle, G., Tobias, R. S. Pseudohalide and chelate complexes of bis(cyclopentadienyl)vanadium(IV). lnorg. Chem., 7: 2479-2484, 1968. Yield: 45%, M.P. 247° C. dcomposition starts. Anal. Calcd. for VC₁₆H₁₇SO₅F₃: C, 44.45; H, 3.96; S, 7.46. Found: C, 44.81; H, 3.99; S, 7.52. UV-Vis: (CH₂Cl₂) λ_(max): 740, 640 (d-d), 370 (LMCT), 309 (π-π* of acac⁻ moiety), 270, 230(π-π* of Cp⁻ rings). IR (KBr Disc): 3118(s), 2295(w), 1564(vs), 1516(vs), 1440(s), 1350(s), 1267(s,b) 1194(w), 1149(vs) 1067(w), 1032(s), 983(w), 959(w), 910(w), 843(vs), 783(vs),756(m), 638(m), 573(vs), 456(s), 408 (m) cm⁻¹.

VCp₂(Hfacac)(O₃SCF₃), (Compound 17). Micro dark green powder was isolated following the procedure described Doyle, G., Tobias, R. S. Pseudohalide and chelate complexes of bis(cyclopentadienyl)vanadium(IV). Inorg. Chem., 7: 2479-2484, 1968. Yield: 20%, M.P. 225° C. decomposition starts. Anal. Calcd.for VC₁₆H₁₁SO₅F₉: C,35.89; H, 2.06; S, 5.98. Found: C, 35.76; H, 2.08; S, 5.89. UV-Vis: (CH₂Cl₂) λ_(max): 700, 557 (d-d), 377 (LMCT), 314 (π-π* of Hfacac⁻ moiety), 271, 244(π-π* of Cp⁻ rings). IR (KBr Disc): 3117(m), 1637(vs), 1597(w), 1552(w), 1523(w), 1446 (s), 1358(w), 1267(s,b) 1194(w), 1149(vs) 1067(w), 1032(s), 983(w), 959(w), 910(w), 843(vs), 783(vs),756(m), 638(m), 573(vs), 456(s), 408 (m) cm⁻¹.

VCp₂(bpy)(O₃SCF₃)₂, (Compound 18). The synthetic procedure was a modified procedure described for TiCp₂ (bpy)(O₃SCF₃)₂. Thewalt, U., Berhalter, K. Kationische Komplexe Mit Der (η⁵—C₅H₅)₂Ti^(IV)-Baugruppe: Darstellung und Struktur Von [(η⁵—C₅H₅)₂ Ti(bpy)]²⁺ (CF₃SO₃ ⁻)₂. J. Organometallic Chem., 302: 193-200, 1986. Light grayish powder was obtained as a precipitate from the THF solution which was collected by filtration and dried. Yield: 38%.M.P.305° C. Anal Calcd. for VC₂₄H₂₀N₂F₆O₆VS: C, 53.1; H, 3.69; N, 2.58; S, 5.9. Found: C, 52.48; H, 3.72; N, 2.51; S, 5.73. UV-Vis (DMSO) λ_(max): 780(sh), 555(d-d), 326(LMCT of Cp₂V²⁺), 272 (sh) (π-π* of Cp ring), 241 (superimposed bands of π-π* of Cp rings and bipyridine) nm. IR (cm-1): 3135(m), 3099(s), 1605(vs), 1504(m), 1477(s), 1452(s), 1437(vs),1307(m), 1257(vs) 1232(vs), 1207(m), 1028(vs), 862(vs), 837(w), 771(vs), 636(vs), 517(vs), 435(vw) cm⁻¹.

Cp₂V(cat), (Compound 19). CP₂VCl₂ (126 mg, 0.50 mmol) was placed in a 250 mL flask and dissolved in THF (100 mL). In another flask the sodium catecholate (Cat) was prepared by the addition of NaH (25 mg, 1.0 mmol, mineral oil had been previously removed by washing with petrolium ether) catechol (to 55.5 mg, 0.50 mmol) in THF (15 mL). The solution was stirred for 2 hours, resulting in a deep blue solution. The catecholate solution was cannulated into the vanadium solution and stirred for 4 hours. The reaction mixture was opened to the air and quickly flash chromatographed under nitrogen on alumina (neutral) (acetonitrile moblie phase). The solvent of the deep blue solution was then removed under vacuum and the product collected. Yield: 26%. M.P. Not determined. Anal. Calcd. for VC₁₆H₁₄O₂: C, 66.45; H, 4.88. Found: C, 66.79; H, 4.93. UV-vis (CH₃ CN) λ_(max): 711(2078), 438 (2041) (LMCT of Cat-V(IV)), 337 (3173) (LMCT of Cp-V(IV)), 292 (8564), 275 (14661), 259 (18945) (π-π* of Cat and Cp rings). IR (KBr pellet): 3100 (w), 3080 (w), 2951 (m), 2945 (w), 2860 (w), 1468 (s), 1438 (m), 1404 (m), 1359 (w), 1261 (vs), 1012 (w), 929 (w), 804 (vs), 638 (w) cm⁻¹.

VCp₂(dtc), (Compound 20). Bis(cyclopendienyle)N, N-diethyl dithiocarbamato triflate salt was prepared according to the published procedure. Casey, A. T., Thackeray, J. R. Dithiochelates of the Bis(h-cyclopentadienyl)vanadium (IV) moiety. II N,N-Dialkyldithiocarbamate and O,O′-dialkyldithiophospahte complexes. Aust. J. Chem. 27: 757-768, 1974. Yield: 90%. M.P. 163° C. Anal. Calcd. for VC₁₆H₂₀S₃F: C, 48.09; H, 3.93; N, 2.75; S, 24.36. Found: C, 48.11; H, 3.97; N, 2.79; S, 24.41. UV-vis (CH₃ CN) λ_(max): 621, 535 (d-d), 392 (LMCT), 330 (Dtc⁻: π-π*), 276, 270, 230 (π-π* of Cp and Dtc⁻). IR (KBr pellet): 3107 (m), 1632 (s), 1595 (w), 1538(w), 1439 (s), 1212 (s), 1201(s), 1156(s), 1123(m), 1019 (s), 855 (s), 641 (s) cm⁻¹.

VCp₂(PH), (Compound 21). The reaction mixture composed of VCp₂Cl₂ (0.2 g, 8 mmol) and AgCF₃SO₃ (0.46 g, 18 mmol) in H₂O (10 mL) was stirred for 2 h and then filtered through fine glass fiit. A solution of N-phenyl benzohydroxamic acid in 5 mL ethanol, 0.85 g, 4.0 mmol, was added to the filtrate with stirring, and the resulting solution was kept for 4 h to complete the precipitation of dark colored compound. These were collected by filtration and throughly washed with diethyl ether and dried for overnight under vacuum. Yield: 38%. M.P. 160° C. Anal Calcd. for VC₂₄H₂₀NF₃O₅S: C, 53.1; H, 3.69; N, 2.58; S, 5.9. Found: C, 52.48; H, 3.72; N, 2.51; S, 5.73. UV-Vis: (CH₂Cl₂) )λ_(max): 680, 501 (d-d), 377 (LMCT), 314 (π-π* of hydroxamate moiety), 261, 233 (π-π* of Cp ring) nm. IR (cm⁻¹): 3345(sb), 3117(s), 1651(mb), 1600(m), 1539((vs), 1495(m), 1450(m), 1300(m), 1281(s), 1244 (vs), 1173(s), 999(m), 758(m), 694((m), 638((s), 578(w), 515(m) cm⁻¹.

VCp₂(H), (Compound 22). This reddish-brown compound was prepared following the procedure applied for the compound (20). D'Cruz, O. J., Ghosh, P., Uckun, F. M. Antitumor activity of chelated complexes of bis(cyclopentadienyl)vanadium(IV). Mol. Hum. Reprod., 4: 683-693, 1998. In the instant synthesis, the reactions were carried out in dry THF instead of H₂O using acethydroxamic acid as ligand. Yield: 52%. M.P. Could not be determined because it absorbs moisture from the air and turns pasty within few minutes. Anal Calcd. for VC₁₃H₁₄NF₃O₅S: C, 38.61; H, 3.46; N, 3.46; S, 7.92. Found: C, 38.12; H, 3.72; N, 3.26; S, 7.81. UV-Vis: (CH₂Cl₂) λ_(max): 710, 550 (d-d), 401 (LMCT), 300 (π-π* of hydroxamate moiety), 261, 233 (π-π* of Cp ring)nm. IR (Kbr Disc): 3345(s,vb), 1695(mb), 1635(m), 1500((vs), 1450(s), 1280(m), 1260(s), 1215 (vs), 1144(s), 959(m), 758(m), 635((m), 540(w), 480(m) cm⁻¹.

V(MeCp)₂Cl₂.0.5 H₂O, (Compound 23). The synthetic procedure is described in the literature. Petersen, J. L., Dahl, L. F. Synthesis and structural characterization by X-ray diffraction and electron paramagnetic resonance single-crystal techniques of V(η⁵—C₅H₄CH₃)₂Cl₂. A study of the spatial distribution of the unpaired electron in a V(η₅—C₅H₅)₂L₂-type complex. J. Am. Chem. Soc., 97: 6422-6433, 1975. The bright green microcrystals were seperated from the HCl saturated CHCl₃ solution. Yield. 25%. Anal Calcd. for VC₁₂H₁₅Cl₂O_(0.5): C, 49.82; H, 5.19; Cl, 24.60. Found: C, 49.92; H, 34.90; Cl, 24.90. UV-Vis (CH₂Cl₂) λ_(max): 760, 659 (d-d), 383 (LMCT of Cp₂V²⁺), 286, 233 (π-π* of MeCp rings), nm. IR (cm-1): 3135(m), 3099(s), 1307(m), 1028(vs), 862(vs), 771(vs), 636(vs), 517(vs) cm⁻¹.

V(Me₅CP)₂Cl₂, (Compound 24). The green solid was isolated from diethylether from a reaction mixture of V(Me₅CP)₂ and PCl₃ as described by Moran, M., Masaguer, J. R., Fernandez, V. Synthesis and characterization of halogen and pseudohalogen derivatives of substituted vanadocenes. J. Organometallic Chem. 291: 311-319, 1985. Yield. 20%. Anal Calcd. for VC₂₀H₃₀Cl₂: C, 61.2; H, 7.5; Cl, 13.0. Found: C, 59.9; H, 7.5; Cl, 13.1. UV-Vis (CH₂Cl₂) λ_(max): 740, 652 (d-d), 440 (LMCT of Cp₂V²⁺), 270, 230 (π-π* of Me₅Cp-rings), nm. IR (Kbr Disc): 3118(s), 1194(w), 1149(m), 1032(s), 959(w), 843(vs), 638(vs) cm⁻¹.

V(Me₅Cp)OCl, (Compound 25). This compound was prepared by following the procedure reported in Aistars, A., Newton, C., Rübensthal, T., Doherty, N. M. Covenient synthesis of dichloro(oxo)(pentamethylcyclopentadienyl)vanadium(V),(η—C₅Me₅)V(O)Cl₂. Organometallics. 16. 1994-1996, 1997. Sublimed green materials of V(Me₅CP)₂Cl₂(24) was dissolved in dry THF and were subjected to purged with O₂ for 8 h. The solvent was removed under vacuum and recrystallized from hexane. Yield. 80%. Anal Calcd. for VC₁₀H₁₅OCl₂: C, 43.98; H, 5.54; Cl, 27.67. Found: C, 43.29; H, 5.62; Cl, 27.54. ¹HNMR, ⁵¹V NMR: δ 2.335 (5×CH ₃). (CH₂Cl₂) (UV-Vis (CH₂Cl₂) λ_(max): 680, 605(LMCT of Oxygen and chloride ligand) 410 (LMCT of Cp to V(O)²⁺) 290, 250 (π-π* of Me₅Cp- ring), nm. IR (Kbr Disc): 3440(b, m), 2962(m), 2906(s), 2858(m), 1621(w), 1487(m), 1437(s), 1375(vs), 1066(s), 1014(m), 960(m), 943(m), 806(m), 744(m), 700(m) cm⁻¹.

In vitro Invasion Assays

The in vitro invasiveness of vanadocene-treated cancer cells was assayed using a previously published method which employs Matrigel-coated Costar 24-well transwell cell culture chambers (“Boyden chambers”) with 8.0-μm-pore polycarbonate filter inserts. Narla R K, Liu X P, Klis D, Uckun F M. Inhibition of human glioblastoma cell adhesion and invasion by 4-(4′-hydroxylphenyl)-amino-6,7-dimethoxyquinazoline (WHI-P131) and4-(3′-bromo-4′-hydroxylphenyl)-amino-6,7-dimethoxyquinazoline (WHI-P154). Clin Cancer Res 4:2463-71, 1998. Albini, A., Iwamoto, Y., Kleinman, H. K., Martin, G. R., Aaronson, S. A., Kozlowski, J. M., and McEwan, R. N. A rapid in vitro assay for quantitating the invasiveness of tumor cells. Cancer Res. 47: 3239-3245, 1987. The chamber filters were coated with 50 μg/ml of Matrigel matrix, incubated overnight at room temperature under a laminar flow hood and stored at 4° C. On the day of the experiment, the coated inserts were rehydrated with 0.5 ml serum-free DMEM containing 0.1% bovine serum albumin for 1-2 hours. To study the effects of vanadocenes VDC and VDSe on invasiveness of cancer cells, exponentially growing cells were incubated with these vanadocenes at various concentrations ranging from 1 μM to 10 μM overnight. The cells were trypsinized, washed twice with serum-free DMEM containing BSA, counted and resuspended at 1×10⁵ cells/ml. 0.5 ml cell suspension containing 5×10⁴ cells in a serum-free DMEM containing vanadocene compounds or vehicle was added to the Matrigel-coated and rehydrated filter inserts. Next, 750 μl of NIH fibroblast conditioned medium was placed as a chemoattractant in 24-well plates and the inserts were placed in wells and incubated at 37° C. for 48 hr. After the incubation period, the filter inserts were removed, the medium was decanted off and the cells on the top side of the filter that did not migrate were scrapped off with a cotton tipped applicator. The invasive cells that migrated to the lower side of the filter were fixed, stained with Hema-3 solutions and counted under microscope. Five to 10 random fields per filter were counted to determine the mean (±SE) values for the invasive fraction. The invasive fractions of cells treated with quinazoline derivatives were compared to those of DMSO treated control cells and the percent inhibition of invasiveness was determined using the formula: % Inhibition=100× (1-Invasive Fraction of Drug-Treated Cells/Invasive Fraction of Control Cells). Each treatment condition was evaluated in duplicate in 3 independent experiments. IC50 values were calculated by non-linear regression analysis using an Graphpad Prism software version 2.0 (Graphpad Software, Inc., San Diego, Calif.).

Apoptosis Assays

A flow cytometric two-color terminal dideoxynucleotidyl transferase (TdT)-mediated digoxigenin-uridine triphosphate (dUTP) nick-end labeling assay (TUNEL) was employed to detect apoptotic nuclei. Gavrieli, Y., Sherman, Y., Ben-Sasson, S. A. Identification of programmed cell death in situ via specific labeling of nuclear DNA fragmentation. J. Cell Biol., 119: 493-501, 1992. Exponentially growing cells (10⁶/ml) were incubated in DMSO alone (0.2%) or treated with 100 μM each of the 16 vanadocenes (VDB, VDC, VMDC, VDI, VDA, VDCN, VDOCN, VDSCN, VDSeCN, VDT, VDCO, VDFe, VD(acac), VDH, VD(dpy), and VD(dtc) in 0.1% DMSO for 24 h. Cells were washed in PBS, fixed in 4% paraformaldehyde in PBS for 15 min on ice. Following two washings in PBS, they were permeabilized with 0.1% Triton X-100 in 0.1% sodium citrate for 2 min on ice, and washed twice in PBS. Labeling of exposed 3′-hydroxyl (3′-OH) ends of fragmented nuclear DNA was performed using TdT and fluorescein isothiocyanate (FITC)-conjugated dUTP according to the manufacturer's recommendations (Boehringer Mannheim, Indianapolis, Ind.). Cells were counterstained with 5 μg/ml PI. Control samples included: (i) untreated cells; (ii) cells incubated with the reaction mixture without the TdT enzyme. Cells were analyzed with a FACS Calibur flow cytometer (Becton Dickinson, Mountain View, Calif.). Relative DNA content (PI) was detected with band-pass filter 585/42, and dUTP incorporation (FITC) was detected with band-pass filter 530/30. Fluorescence was compensated for in the acquisition software using single-label control samples. Data were acquired in listmode, gated to 10,000 events per sample, and analyzed with the use of CELLQuest software program (Becton Dickinson). Nonapoptotic cells do not incorporate significant amounts of dUTP due to lack of exposed 3′-OH ends, and consequently have relatively little or no fluorescence compared to apoptotic cells which have an abundance of 3′-OH (M2 gates). Vanadocene-induced apoptosis is shown by an increase in the number of cells staining with FITC-dUTP. The M1 and M2 gates were used to demarcate non-apoptotic and apoptotic PI-counterstained cell populations, respectively. TUNEL assays were performed using two testicular cell lines Tera-2 and Ntera-2 following exposure to each of the 16 vanadocenes. In other experiments, MC540 binding (as an early marker of apoptosis) and PI permeability (as a marker of advanced stage apoptosis) were simultaneously measured in human cancer cells 24 hours after exposure to vanadocenes, as previously described. Uckun, F. M., Narla, R. K., Jun, X., Zeren, T., Venkatachalam, T., Waddick, K. G., Rostostev, A., Myers, D. E. Cytotoxic activity of EGF-genstein against breast cancer cells. Clin. Cancer Res. 4:901-912, 1998. Vassilev, A., Ozer, Z., Navara, C., Mahajan, S., and Uckun, F. M. Bruton's tyrosine kinase as an inhibitor of the Fas/CD95 death-inducing signaling complex. J. Biol. Chem. 274:1646-56, 1999. Whole cells were analyzed using a FACStar Plus flow cytometer (Becton Dickinson, San Jose, Calif.). All analyses were done using 488 nm excitation from an argon laser. MC540 and PI emissions were split with a 600 nm short pass dichroic mirror and a 575 nm band pass filter was placed in front of one photomultiplier tube to measure MC540 emission and a 635 nm band pass filter was used for PI emission.

Morphological evidence for apoptosis was sought among the TUNEL-positive cells using confocal laser scanning microscopy (CLSM). Confocal microscopy was performed using BioRad MRC-1024 Laser Scanning Confocal Microscope (BioRad, Hercules, Calif.) equipped with a krypton/argon mixed gas laser (excitation lines at 488, 568, and 647 nm) and mounted on a Nikon Eclipse E800 series upright microscope equipped with high numerical objectives. Using fluorescence imaging, the fluorescence emission of FITC and PI from nuclei of in Ntera-2 cells was simultaneously recorded using 598/40 nm, and 680 DF32 emission filter respectively. Confocal images were obtained using a Nikon 60× (NA 1.4) objective and Kalman collection filter. Digitized images were saved on a Jaz disk (Iomega Corp., Roy, Utah) and processed with the Adobe Photoshop software (Adobe Systems, Mountain View, Calif.). Final images were printed using a Fuji Pictography 3000 (Fuji Photo Film Co., Tokyo, Japan) color printer.

In other experiments, TERA-2 and NTREA-2 cells were plated at 50% confluency in T-150 flasks in media supplemented with 10% FCS; 24 h later, they were exposed to vehicle (0.05% DMSO) or 100 μM each of the 6 representative vanadocenes (VDC, VDO, VDSCN, VDSeCN, VDT, and VD(dtc) in 0.05% DMSO. Combined adherent and nonadherent cells (5×10⁶/sample) were harvested at 24 h and washed in PBS. DNA was prepared from Triton-X-100 lysates for analysis of fragmentation. Uckun, F. M., Evans, W. E., Forsyth, C. J., Waddick, K. G., Tuel-Ahlgren, L., Chelstrom, L. M., Burkhardt, A., Bolen, J., Myers, D. E. Biotherapy of B-cell precursor leukemia by targeting genistein to CD19-associated tyrosine kinase. Science (Washington D.C.) 267:886-91, 1995. Uckun, F. M., Narla, R. K., Jun, X., Zeren, T., Venkatachalam, T., Waddick, K. G., Rostostev, A., Myers, D. E. Cytotoxic activity of EGF-genstein against breast cancer cells. Clin. Cancer Res. 4:901-912, 1998. In brief, cells were lysed in hypotonic 10 mmol/L Tris-HCl (pH 7.4), 1 mmol/L EDTA, 0.2% Triton-X-100 detergent; and subsequently centrifuged at 11,000 g. To detect apoptosis-associated DNA fragmentation, supernatants were electrophoresced on a 1.2% agarose gel, and the DNA fragments were visualized by ultraviolet light after staining with ethidium bromide. In additional experiments, (a) leukemia cell lines NALM-6, MOLT-3, and HL-60, (b) glioblastoma cell lines U373 and U87, and (c) breast cancer cell lines MDA-MB-231 and BT-20 were exposed to multiple concentrations of VDC and VDSeCN and then assayed for apoptosis by DNA gels as well as flow cytometry.

In some experiments, immunofluorescence was used to examine the morphologic features of vanadocene-treated cancer cells. At the end of the indicated treatment period, cells were washed twice with PBS and fixed in 2% paraformaldehyde. The cells were permeabilized and non-specific binding sites were blocked with 2.5% BSA in PBS containing 0.1% Triton X-100 for 30 min. Tubulin expression was examined by immunofluorescence using a monoclonal antibody against α-tubulin (Sigma Chemical Co, St. Louis, Mo.) at a dilution of 1:1000 and an anti-mouse IgG conjugated to FITC. Cells were washed in PBS and counterstained with toto-3 (Molecular Probes Inc., Eugene, Oreg.) for 10 min at a dilution of 1:1000. Cells were washed again with PBS and the coverslips were mounted with Vectashield (Vector Labs, Burlingame, Calif.) and viewed with a confocal microscope (Bio-Rad MRC 1024) mounted in a Nikon Labhophot upright microscope. Digital images were saved on a Jaz disk and processed with Adobe Photoshop software (Adobe Systems, Mountain View, Calif.).

Oxovanadium

Cytotoxicity Assays

The cytotoxicity of oxovanadium (IV) complexes listed in Table 6 were tested against 9 different human cancer cell lines was performed using the MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide) assay (Boehringer Mannheim Corp., Indianapolis, Ind.) as described previously (20). Briefly, exponentially growing tumor cells were seeded into a 96-well plate at a density of 4×10⁴cells/well and incubated with medium containing the oxovanadium(IV) compounds concentrations ranging from 0.1 to 250 μM for 48 hours at 37° C. in a humidified 5% CO₂ atmosphere. Triplicate wells were used for each treatment. To each well, 10 μl of MTT (0.5 mg/ml final concentration) was added and the plates were incubated at 37° C. for 4 hours to allow MTT to form formazan crystals by reacting with metabolically active cells. The formazan crystals were solubilized overnight at 37° C. in a solution containing 10% SDS in 0.01 M HCl. The absorbence of each well was measured in a microplate reader (Labsystems) at 540 nm and a reference wavelength of 690 nm. To translate the OD 540 values into the number of live cells in each well, the OD₅₄₀ values were compared to those on standard OD₅₄₀—versus-cell number curves generated for each cell line. The percent survival was calculated using the formula: % survival=Live cell number[test]/Live cell number [control]×100. The IC₅₀ values were calculated by non-linear regression analysis using an Graphpad Prism software version 2.0 (Graphpad Software, Inc., San Diego, Calif.).

In situ Detection of Apoptosis

The demonstration of apoptosis was performed as described earlier (20, 21) by the in situ nick-end-labeling method using in situ cell death detection kit (Boehringer Mannheim Corp., Indianapolis, Ind.) according to the manufacturer's recommendations. Exponentially growing cells were seeded in 6-well tissue culture plates and incubated with fresh medium containing compounds. After a 24 hour incubation at 37° C. in a humidified 5% Co₂ incubator the cells were collected into a 15 ml centrifuge tube, washed with PBS and pelleted by centrifugation at 1000 rpm for 5 min. The cells were fixed in 2% paraformaldehyde, washed with PBS and pelleted by centrifuging the tubes at 1000 rpm for 5 min. Cells pellets were resuspended in 50 μl of PBS, transferred to superforst plus slides and allowed to attach for 15 min. The cells were permeabilized with 0.1% triton X-100 in 0.1% citrate buffer and incubated for 1 hr at 37° C. with the reaction mixture containing terminal deoxynucleotidyl transferase (TdT) and fluorescein isothiocyanate (FITC)-conjugated dUTP. Cells were washed with PBS to remove unbound reagents and the coverslips were mounted onto slides with Vectashield containing propidium iodide (Vector Labs, Burlingame, Calif.) and slides were viewed with a confocal laser scanning microscope. Non-apoptotic cells do not incorporate significant amounts of dUTP due to lack of exposed 3-hydroxyl ends, and consequently have much less fluorescence than apoptotic cells which have an abundance of exposed 3′-hydroxyl ends. In control reactions, the TdT enzyme was omitted from the reaction mixture.

Mitochondrial Transmembrane Potential Assessment

To measure the changes in mitochondria, NALM-6 cells were incubated with compound 29 at concentrations ranging from 0.1 μM to 1 μM for 24 hr, 48 hr, 72 hr or 96 hr, stained with specific fluorescent dyes and analyzed with flow cytometer. Mitochondrial membrane potential (ΔΨm) was measured using two dyes including a lipophollic cation 5,5′,6,6′-tetrachloro-1,1′,3,3′-tetraethlybenzimidazolylcarbocyanine iodide (JC-1; Molecular probes, Eugene, Oreg.) and a cyanine dye, 1,1′,3,3,3′,3′-hexamethylindodicarbocyanine iodide [DiIC₁(5); Molecular probes] as earlier described (22). JC-1 can enter the cells, and selectively mitochondria, and has been used to assess ΔΨm in a variety of studies (23,24). JC-1 is a monomer at 527 nm after being excited at 490 nm; with polarization of ΔΨm, J-aggregates are formed that shift emission to 590 nm (23, 24). This can be detected on a flow cytometer by assessing the green signal (at 527 nm) and green-orange signal (at 590 nm) simultaneously, creating an index of the number of cells polarized and depolarized mitochondria. The treated and control cells were washed and plated in a 6-well plate at 1×10⁶ cells in fresh medium. JC-1 was added at a concentration of 10 μg/ml, and cells were incubated for 10 min in the dark at room temp. Cells were then washed twice with ice-cold PBS and immediately analyzed using Becton Dickinson (San Jose, Calif.) Calibur flow cytometer. At least 2×10³cells were analyzed to determine the percentage of cells with polarized and depolarized mitochondria. DiIC1(5), a cyanine dye is amphioatheic and cationic that concentrate in energized mitochondria and has been used in a variety of studies to measure the mitochondrial membrane potential (25-27). NALM-6 cells were stained with DiIC₁(5) at 40 nM concentration for 30 min in the dark as described for JC-1. The cells were analyzed using Vantage Becton Dickinson cell sorter equipped with HeNe laser with excitation at 635 nm and the fluorescence was collected at 666 nm.

Mitochondrial Mass Determination

Relative mitochondrial mass was measured by using Becton Dickinson Calibur flow cytometry and the fluorescent stain 10-n-nonyl-acridine orange (NAO), which binds the mitochondrial phospholipid cardiolipin, that has been extensively used to provide an index of mitochondrial mass (28). 1×10⁶ compound 29-treated NALM-6 cells at concentrations of 0.1 μM to 1 μM for 24 hr, 48 hr, 72 hr, or 96 hr were incubated with 30 μM of NAO in complete medium for 10 min at room temp in the dark, washed with ice-cold PBS and analyzed using log scale photomultiplier to detect the green fluorescence at 527 nm. Relative change in the mitochondrial mass was measured using the mean fluorescence value of mitochondria of compound 29-treated and vehicle-treated cells.

Quantitative Apoptosis Assays

A flow cytometric two-color terminal dideoxynucleotidyl transferase (TdT) mediated digoxigenin-uridine triphosphate (dUTP) nick-end labeling assay (TUNEL) was employed to detect apoptotic nuclei. Edelman, G. M. Adhesion and counteradhesion: morphogenetic functions of the cell surface. Prog. Brain Res. 101:1-14, 1994. Exponentially growing cells (10⁶/ml) were incubated in DMSO alone (0.1%) or treated with 50 μM each of the 15 oxovanadium compounds in 0.1% DMSO for 24 h. Cells were washed in PBS, fixed in 4% paraformaldehyde in PBS for 15 min on ice. Following two washings in PBS, they were permneabilized with 0.1% Triton X-100 in 0.1% sodium citrate for 2 min on ice, and washed twice in PBS. Labeling of exposed 3′-hydroxyl (3′-OH) ends of fragmented nuclear DNA was performed using TdT and fluorescein isothiocyanate (FITC)-conjugated dUTP according to the manufacturer's recommendations (Boehringer Mannheim, Indianapolis, Ind.). Cells were counterstained with 5 μg/ml PI. Control samples included: (i) untreated cells; (ii) cells incubated with the reaction mixture without the TdT enzyme. Cells were analyzed with a FACS Calibur flow cytometer (Becton Dickinson, Mountain View, Calif.). Relative DNA content (PI) was detected with band-pass filter 585/42, and dUTP incorporation (FITC) was detected with band-pass filter 530/30. Fluorescence was compensated for in the acquisition software using single-label control samples. Data were acquired in listmode, gated to 10,000 events per sample, and analyzed with the use of CELLQuest software program (Becton Dickinson). Nonapoptotic cells do not incorporate significant amounts of dUTP due to lack of exposed 3′-OH ends, and consequently have relatively little or no fluorescence compared to apoptotic cells which have an abundance of 3′-OH (M2 gates). Oxovanadium compounds-induced apoptosis is shown by an increase in the number of cells staining with FITC-dUTP. The M1 and M2 gates were used to demarcate non-apoptotic and apoptotic PI-counterstained cell populations, respectively.

RESULTS Vanadocene Compounds

Synthesis and Characterization of Vanadocene Compounds.

The chemical structures and physical data (viz., UV-vis spectral data, infrared spectral data, and elemental analysis results) of compounds 1-25 are detailed in Table 1, Table 2, Table 3, and Table 4.

Cytotoxic Effects of Vanadocenes on Human Testicular Cancer Cells

Using the mitochondrial function-based MTT viability assay, the effects of 5 metallocene dichlorides containing vanadium (VDC), titanium (TDC), zirconium (ZDC), molybdenum (MDC), or haffium (HDC), on two human testicular cancer cell lines, Tera-2 and Ntera-2, were tested by measuring cellular proliferation at 7 different concentrations ranging from 1.9 μM to 250 μM for 24 h (FIG. 1). Only vanadium-containing metallocene, VDC, inhibited the growth of both cell lines with IC₅₀ values of 80.6 μM and 74.0 μM, respectively. Surprisingly, other metallocene dichlorides containing titanium, zirconium, molybdenum or hafnium as central metal atom (oxidation state IV), had no effect on cell proliferation even at 250 μM (Table 5). These results demonstrate that the vanadium(IV)-containing bis(cyclopentadienyl)-metal complex has cytotoxic activity against human testicular cancer cells.

Sixteen structurally similar compounds with differing substituents around the ancillary position of the Cp₂-vanadium(IV) unit were examined for their growth-inhibiting properties. These vanadocene complexes included: 4 vanadocene dihalides (VDB, VDC, VMDC, and VDI), 5 vanadocene di-pseudohalides (VDA, VDCN, VDOCN, VDSCN, and VDSeCN), 3 vanadocene disubstituted derivatives (VDT, VDCO, and VDFe), and 4 chelated vanadocenes (VD(acac), VDH, VD(bpy), and VD(atc)). The cytotoxic effects of these vanadocenes were tested at 7 different concentrations (1.9 μM to 250 μM). Each one of the 4 vanadocene dihalides, 5 vanadocene di-pseudohalides, 3 vanadocene disubstituted derivatives, and 4 chelated vanadocenes with various substituents covalently coordinated as ligands to the central metal ion vanadium (IV) induced a concentration-dependent cytotoxicity to both Tera-2 and Ntera-2 cells at micromolar concentrations. However, marked differences were noted in their potency.

The IC₅₀ values of VDB, VDC, VMDC, VDI, VDA, VDCN, VDOCN, VDSCN, VDSeCN, VDT, VDCO, VDFe, VD(acac), VDH, VD(BPY), and VD(DTC) calculated from concentration-response curves for the two cell lines are shown in Table 5. The IC₅₀ values for the 16 vanadocenes evaluated ranged from 9 to 221 μM. In general, vanadocenes were less potent than cisplatin (IC₅₀=˜5 μM). However, the cytotoxic effects of the most potent vanadocenes, VDSCN and VDSeCN, were comparable to those of cisplatin (IC₅₀ values˜9-22 μM) when tested side-by-side under identical experimental conditions. The variable potency of vanadocenes suggest that the various mono and bidentate ligand groups affect the cytotoxic activity of these compounds. The potential cytotoxic effects of vanadium [vanadyl(IV) sulfate] were tested at the same concentrations. In sharp contrast to the organometallic compounds containing vanadium(IV), inorganic vanadium (oxidation state IV) salt lacked cytotoxic activity even at 250 μM (Table 5). Importantly, the anticancer activity of these compounds was not restricted to testicular cancer cells. Both compounds also killed human glioblastoma cells at low micromolar concentrations (Table 5).

Vanadocenes Induce Apoptosis in Human Testicular Cancer Cells

In order to determine if the cytotoxicity of vanadocenes is associated with apoptotic cell death, Tera-2 and Ntera-2 cells were cultured with vanadocenes (100 μM) for 24 h and then subjected to flow cytometric analysis for dUTP incorporation by the TdT-mediated TUNEL assay. FIGS. 2 and 3 depict the two-color flow cytometric contour plots of cells from representative TUNEL assays. Control Tera-2 and Ntera-2 cells were treated for 24 hours at 37° C. with 0.1% DMSO whereas test cells were treated for 24 hours at 37° C. with a vanadocene compound at 100 μM final concentration. The TdT-dependent incorporation of FITC-dUTP was dramatically increased in vanadocene-treated cells as a result of abundance of free 3′-hydroxyl DNA ends created by endonuclease-mediated DNA fragmentation. Among the 16 vanadocenes evaluated by the flow cytometric TUNEL assay, 15 caused a marked increase in TUNEL-positive nuclei ranging from 44.5% to 88% for Tera-2 cells and 38.7% to 99.6% for Ntera-2 cells respectively (Table 5).

FIGS. 2 and 3 also depict the two-color confocal microscopy images of DMSO treated control cells and vanadocene-treated test cells. Vanadocene-treated cells showed dual fluorescence, consistent with apoptosis. Furthermore, vanadocene-treated cells displayed the characteristic morphologic features of apoptotic cell death, including cellular shrinkage, chromatin condensation, and the appearance of typical apoptotic bodies. Apoptosis after vanadocene treatment was also evident from the concentration-dependent emergence of a hypodiploid (<2N) peak in the DNA histograms of PI-stained cells, which was accompanied by nonselective loss of G0/1, S, and G2M phase cells (FIG. 4).

Cytotoxic Activity of Vanadocene Compounds Against Human Glioblastoma, Leukemia, and Breast Cancer Cell Lines

In MTT assays, both U373 glioblastoma cells (Table 5 and FIG. 5) and NALM-6 B-lineage acute lymphoblastic leukemia (ALL) cells (Table 5) were found to be sensitive to the cytotoxic activity of vanadocenes. Similar to testicular cancer cells, glioblastoma cells were sensitive to VDC but not to other metallocene dichlorides (Table 5). Interestingly, VDI and VD(dtc) were >1-log more active against U373 cells than they were against TERA-2 or NTERA-2 cells. VDSeCN which was the most active vanadocene compound against testicular cancer cells was found to be the most active vanadocene compound against glioblastoma cells as well (Table 5, FIG. 5). Only 4 vanadocenes (VDC, VDB, VDI, VDA, VDSeCN) were tested against NALM-6 leukemia cells and all 4 were active and VDSeCN was the most potent (Table 5).

To determine whether the cytotoxicity of vanadocenes against non-testicular cancer cells was also associated with apoptosis, MC540 binding (as an early marker of apoptosis) and PI permeability (as a marker of advanced stage apoptosis) were simultaneously measured in HL60 acute myeloid leukemia (AML), MDA-MB231 and BT-20 breast cancer, as well as U87 glioblastoma cells 24 hours after exposure to the lead vanadocene compound VDSeCN. As shown in FIG. 6, VDSeCN induced apoptosis in all 4 cell lines in a concentration-dependent fashion. At 100 μM, 51% of HL-60 cells, 67% of MDA-MB-231 cells, 40% of BT-20 cells, and 79% of U87 cells showed dual MC540/PI fluorescence consistent with advanced stage apoptosis. The total percentage of apoptotic cells (both early MC540⁺PI⁻ and advanced stage MC540⁺PI⁺) at this concentration were 98% for HL-60 cells, 72% for MDA-MB-231 cells, 61% for BT-20 cells, and 90% for U87 cells (FIG. 6). Apoptosis after both VDSeCN and VDC treatment was also evident from the concentration-dependent emergence of a hypodiploid (<2N) peak in the DNA histograms of PI-stained HL-60 leukemia cells, which was accompanied by nonselective loss of G0/1, S, and G2M phase cells (FIG. 7).

Immunofluorescence staining with anti-α-tubulin antibody and the nuclear dye toto-3 in combination with confocal laser scanning microscopy was performed to examine the morphological features of BT-20 breast cancer cells treated with VDC. After 48-72 hr of exposure to 25 μM VDC, most of the BT-20 cells showed an abnormal architecture with complete disruption of microtubules, marked shrinkage, nuclear fragmentation and inability to adhere to the substratum (FIG. 8). The cytotoxic effects of metallocene compounds were systematically assessed, including 16 vanadocene diacido complexes against human testicular cancer cells. Vanadoces exhibited significant cytotoxicity against testicular cancer cells and induced apoptosis within 24 hours. Vanadocenes with dithiocyanate (VDSCN) and diselenocyanate (VDSeCN) as ancillary ligands were identified as the most potent cytotoxic compounds. Vanadocenes were capable of inducing apoptosis not only in testicular cancer cells, but in ALL, AML, breast cancer, and glioblastoma cells as well. Thus, the potent cytotoxic activity of vanadocene compounds was not limited to testicular cancer cells. The lead compound VDSeCN may be useful as an anti-cancer agent.

Among the five metallocenes evaluated, only vanadium (IV)-containing complexes exhibit cytotoxicity against human testicular cancer cells. Biological evaluation of a novel series of systematically coordinated vanadocenes with dihalide, pseudodihalide, disubstituted derivatives, and chelated ancillary ligands demonstrated that the cytotoxic potency of vanadocenes can be modulated by the coordinated ligands. All 16 vanadocenes tested side-by-side induced apoptosis of testicular cancer cells as shown by increased dUTP incorporation into nuclear DNA. Confocal microscopy images confirmed the results of dUTP incorporation in the nuclei of representative vanadocene-treated cells. In contrast, the inorganic vanadium(IV) compound, vanadyl sulfate, had no cytotoxic effects on testicular cancer cells. Thus, although the cytotoxic effect of vanadocenes was primarily dependent upon the central vanadium(IV) ion, the two cyclopentadienyl units attached to vanadium(IV) coordination sites, and the various mono and bidentated ligand groups coordinated to the bis(cyclopentadienyl)vanadium (IV) moiety appear to be also very important for their anticancer activity.

Metallocene diacido complexes, especially titanocene dichloride and vanadocene dichloride may be useful as a chemopreventive agent and has been found to be active against development of mammary, lung, colon, skin, as well as against various human tumors heterotransplanted to athymic mice. Köpf-Maier, P., Kopf, H. Tumor inhibition by titanocene complexes: activity against B16 melanoma and colon 38 carcinoma. Arzneim-Forsch/Drug Res., 37. 532-534, 1987. Moebus, V. J., Stein, R., Kieback, D. G., Runnebaum, I. B., Sass, G., Kreienberg, R. Antitumor activity of new organometallic compounds in human ovarian cancer cell lines and comparison to platin derivatives. Anticancer Res., 17: 815-822, 1997. Surprisingly, unlike vanadocenes, TDC as well as other non-vanadium(IV)-containing metallocenes had no effect on the growth of testicular cancer cells. Therefore, it is likely that the mechanism of vanadocene-mediated growth inhibition is different from that induced by titanocene or other metallocenes reported in other types of cancer cells. Köpf-Maier, P., Kopf, H. Tumor inhibition by titanocene complexes: activity against B16 melanoma and colon 38 carcinoma. Arzneim-Forsch/Drug Res., 37: 532-534, 1987. Köpf-Maier, P. Tumor inhibition by titanocene complexes: influence upon two xenografted human lung carcinomas. J. Cancer Res. Clin. Oncol., 113. 342-348, 1987. McLauglin, M. L., Cronan, J. M., Schaller, T. R., Snelling, R. D. DNA-metal binding by antitumor-active metallocene dichlorides from inductively coupled plasma spectroscopy analysis: Titanocene dichloride forms DNA-CP₂Ti or DNA-CpTi adducts depending on pH. J. Am. Chem. Soc., 112. 8949-8952, 1990. This difference observed between TDC and VDC is most likely due to structural orientation as well as the one electron configuration of TDC when compared to vanadocenes such as VDC. In addition, unlike other transition metals, vanadium(IV)-containing metallocenes can have pleiotropic effects in cells such as modulation of the cellular redox potential, Rehder, D. The bioinorganic chemistry of vanadium. Angew Chem. Int. Ed. Engl., 30: 148-167, 1991, and Choukroun, R., Douziech, B., Pan, C., Dahan, F., Cassoux, P. Redox properties of cationic vanadium(IV): [Cp₂VCH₃(CH₃CN)][BPh₄]. Oraganometallics, 14: 4471-4473, 1995, increased phosphorylation, Heffetz, D., Bushkin, I., Dror, R., Zick, Y. The insulinomimetic agents H202 and vanadate stimulate protein tyrosine phosphorylation in intact cells. J. Biol. Chem., 265: 2896-2902, 1990. Stem, A., Yin, X., Tsang, S. S., Davison, A., Moon, J. Vanadium as a modulator of cellular regulatory cascades and oncogene expression. Biochem. Cell Biol., 71: 103-112, 1993, and generation of reactive oxygen intermediates. Byczkowski, J. Z., Wan, J. Z., Kulkarni, A. P. Vanadium-mediated lipid peroxidation in microsomes from human term placenta. Bull. Environ. Contam. Toxicol., 41: 696-703, 1988. Ozawa, T., Hanaki, A. ESR evidence for the formation of hydroxyl radicals during the reaction of vanadyl ions with hydrogen peroxide. Chem. Pharm. Bull., 377: 1407-1409, 1989. Carmichael, A. J. Vanadyl-induced Fenton like reaction in RNA: an ESR and spin trapping study. FEBS Lett., 261: 165-170, 1990. Younes, M., Strubelt, O. Vanadate-induced toxicity towards isolated perfused rat livers: The role of lipid peroxidation. Toxicology, 66:63-74, 1991. Keller, J., Sharma, R. P., Grover, T. A., Piette, L. H. Vanadium and lipid peroxidation: Evidence of involvement of vanadyl and hydroxyl radical. Arch. Biochem. Biophys. 265: 524-533, 1988. Sakurai, H., Nakai, M., Miki, T., Tsuchiya, K., Takada, J., Matsushita, R. DNA cleavage by hydroxyl radicals generated in a vanadyl ion-hydrogen peroxide system. Biochem. Biophys. Res. Commun. 189: 1090-1095, 1992. Sakurai, H., Tamura, H., Okatani, K. Mechanism for a new antitumor vanadium complex hydroxyl radical-dependent DNA-cleavage by 1,10-phenanthroline-vanadyl complex in the presence of hydrogen peroxide. Biochem. Biophys. Res. Commun., 206. 133-137, 1995. Shi, X., Wang, P., Jiang, H., Mao, Y., Ahmed, N., Dalal, N. Vanadium(IV) causes 2′-deoxyguanosine hydroxylation and deoxyribonucleic acid damage via free radical reactions. Ann. Clin. Lab. Sci. 26: 39-49, 1996.

The potential therapeutic applications of organovanadium compounds including vanadocenes in vivo, particularly to suppress tumor cell growth via apoptosis, reduce hyperlipidemia, and hypertension via tyrosine kinase-signalling pathways with relatively few adverse effects has sparked interest as a new class of pharmacological agents. Eliopoulos, A. G., Kerr, D. J., Maurer, H. R., Hilgard, P., Spandidos, D.A. Induction of the myc but not CH-ras promoter by platinum compounds. Biochem. Pharmacol. 50: 33-38, 1995. Orvig, C., Thompson, K. H., Battel, M., McNeill, J. H. Vanadium compounds as insulin mimetics. In: Sigel H, Sigel A, eds. Metal ions in biological systems. New York:Marcel Dekker 31: 595-616, 1995. Tsiani, E., Fantus, I. G. Vanadium compounds: biological actions and potential as pharmacological agents. Trends Endocrinol. Metab. 8: 51-58, 1997. Nechay, B. R. Mechanisms of action of vanadium. Annu. Rev. Pharmacol. Toxicol. 24: 501-524, 1984. The apoptosis-inducing cytotoxic effects of novel vanadocenes against human cancer cells reported herein indicate that vanadocenes may be useful as anticancer agents. TABLE 1 Vanadocene Compounds - Type 1 Series UV-vis [λ(nm); IR Spectral Data Elemental Analysais # Compound Chemical Structure Solvent] [cm⁻¹] [Found(Calcd.)] 1 HDC

312, 268, 232 (CH₂Cl₂) 3105(vs), 1439(vs), 1365(m), 1126(m), 1014(vs), 920(s,d), 802(vs), 816(vs), 611(m) C, 32.09(31.62) H, 2.75(2.63) Cl, 18.98(18.71) 2 MDC

678, 436, 299, 283, 267 (DMSO) 3093(vs), 1420(vs), 1375(m), 1100(m), 1060(m), 825(vs), 590(m) C, 40.8(40.4) H, 3.39(3.37) Cl, 24.4(23.9) 3 TDC

526, 391, 314, 255 (CH₂Cl₂) 3105(vs), 1441(vs), 1368(m), 1130(m), 1016(vs), 956(m), 872(s), 820(s) C, 48.56(48.2) H, 4.03(4.01) Cl, 28.78(28.5) 4 ZDC

341, 294, 236 (CH₂Cl₂) 3104(vs), 1435(s), 1363(m), 1122(s), 1014(s), 815(s), 610(m) C, 41.01(41.09) H, 3.4(3.4) Cl, 24.84(24.31) 5 VDC

767, 647, 380, 283, 244 (CH₂Cl₂) 3095(vs), 1444(s), 1433(s), 1130(m), 1070(m), 887(m), 825(vs) C, 47.88(47.62) H, 4.04(3.97) Cl, 27.64(28.1)

TABLE 2 Vanadocene Compounds - Type 2 Series UV-vis [λ(nm); IR Spectral Data Elemental Analysais # Compound Chemical Structure Solvent] [cm⁻¹] [Found(Calcd.)] 6 VDB

733, 412, 298,232 (CH₂Cl₂) 3089(vs), 1425(s), 1431(m), 1373(m), 1363(w), 1128(w), 1024(m), 1014(m), 825(vs) C, 35.19(35.19) H, 2.9(2.92) Br, 46.91(46.92) 7 VDI

620, 552, 352, 296, 232 (CH₂Cl₂) 3095(s), 1425(s), 1373(m), 1182(m), 1024(m), 1014(m), 825(vs) C, 28.1(27.58) H, 2.42(2.3) I, 58.4(58.9) 8 VDA

434, 314, 257, 233 (CH₂Cl₂) 3114(vs), 1448(m), 1375(m), 1126(w), 1080(s), 1024(m), 835(vs), 590(m) C, 45.28(45.28) H, 3.73(3.77) N, 31.16(31.2) 9 VDN

605, 394, 307, 250 (CH₂Cl₂) 3114(vs), 2120(s), 2110(s), 1435(s), 1420(s), 1126(m), 1014(s), 881(s), 848(s), 845(s) C, 60.98(61.89) H, 4.30(4.29) N, 11.45(12.00) 10 VDO

742, 373, 277, 237 (CH₂Cl₂) 3531(m), 3110(m), 2248(vs), 2217(vs), 1444(s), 1330(s), 1024(w), 833(vs), 603(s), 593(s) C, 53.85(54.3) H, 3.97(3.8) N, 10.2(10.6) 11 VDOCN

710, 490, 257, 227 (CH₂Cl₂) 3110(m), 2657(w), 2117(vs), 1444(m), 1330(s), 1261(w), 1018(m), 950(m), 833(vs), 635(vs), 424(w) C, 51.35(51.06) H, 3.97(3.87) N, 5.65(5.41) Cl, 13.45(13.73) 12 VDS

739, 463, 401, 270, 251 (CH₂Cl₂) 3087(s), 2086(vs), 2067(vs), 1433(s), 1423(m), 1010(m), 840(vs), 480(vw) C, 47.55(47.05) H, 3.26(3.59) S, 20.91(20.91) 13 VDSe

716, 488, 456, 270, 251 (CH₂Cl₂) 3076(s), 2085(vs), 2065(vs), 1444(m), 1431(s), 1074(w), 1008(m), 962(m), 843(vs) C, 36.85(36.83) H, 2.64(2.56) N, 6.97(7.1) 14 VDFe

648, 575, 362, 311, 265, 240 (CH₂Cl₂) 3109(m), 2924(m), 2318(s), 2289(m), 1622(m), 1447(s), 1435(m), 1358(w), 1027(s), 1012(s), 856(s), 846(s) C, 31.2(31.6) H, 2.56(2.9) N, 3.48(3.1) Cl, 40.31(39.98) 15 VDT

740, 640, 370, 309, 270, 230 (CH₂Cl₂) 3118(s), 1564(vs), 1440(s), 1350(s), 1218(s), 1194(w), 1149(vs), 1032(s), 959(w), 843(vs), 638(vs) C, 44.81(44.45) H, 3.99(3.96) S, 7.52(7.46)

TABLE 3 Vanadocene Compounds - Type 3 Series UV-vis [λ(nm); IR Spectral Data Elemental Analysais # Compound Chemical Structure Solvent] [cm⁻¹] [Found(Calcd.)] 16 VD(acac)

740, 640, 370, 309, 270, 230 (CH₂Cl₂) 3118(s), 2295(w), 1564(vs), 1440(s), 1350(s), 1267(sb), 1218(s), 1194(w), 1149(vs), 1032(s), 983(w), 910(w), 843(s), 573(s) C, 44.81(44.45) H, 3.99(3.96) S, 7.52(7.46) 17 VD(hƒ-acac)

575,377, 314, 271, 244 (CH₂Cl₂) 3117(m), 1637(vs), 1597(w), 1552(w), 1446(s), 1260(vs), 1219(vs), 1163(vs), 1142(s), 1120(m), 1030(vs), 851(s), 640(vs) C, 35.76(35.89) H, 2.08(2.06) S, 5.89(5.98) 18 VD(bpy)

780, 326, 272, 241 (CH₂Cl₂) 3135(m), 3099(s), 1605(s), 1504(m), 1477(m), 1452(s), 1437(vs), 1307(m), 1257(vs), 1232(vs), 1028(vs), 862(vs), 771(vs), 636(vs) C, 52.48(53.1) H, 3.72(3.69) N, 2.51(2.58) S, 5.73(5.9) 19 VD(cat)

711, 438, 337, 292, 275, 259 (CH₂Cl₂) 3100(w), 3080(w), 2951(m), 2945(w), 2860(w), 1468(s), 1438(m), 1404(m), 1359(w), 1261(vs), 1012(w), 804(vs), 638(w). C, 66.79(66.45) H, 4.93(4.88) 20 VD(dtc)

621, 535, 392, 330, 276, 270, 230 (CH₃CN) 3107(m), 1632(s), 1595(w), 1538(w), 1439(s), 1212(s), 1201(s), 1156(s), 1123(m), 1019(s), 855(s), 641(s) C, 43.41(43.31) H, 4.14(4.18) N, 2.86(2.93) S, 19.98(20.08) 21 VDPH

680, 501, 377, 314, 261, 233 (CH₂Cl₂) 3117(s), 1600(m), 1539(s), 1495(m), 1450(m), 1300(m), 1281(s), 1244(s), 1173(s), 999(m), 758(m), 694(m), 638(s) C, 36.85(36.83) H, 2.64(2.56) N, 6.97(7.1) 22 VDH

710, 550, 401, 300, 261, 233 (CH₂Cl₂) 1695(mb), 1635(m), 1500(vs), 1450(s), 1280(s), 1260(s), 1215(vs)1144(s), 959(m), 758(m), 635(m), 540(w), 480(m) C, 38.12(38.61) H, 3.72(3.46) N, 3.26(3.46)

TABLE 4 Vanadocene Compounds - Type 4 Series UV-vis [λ(nm); IR Spectral Data Elemental Analysais # Compound Chemical Structure Solvent] [cm⁻¹] [Found(Calcd.)] 23 VMDC

760, 659, 383, 286, 233 (CH₂Cl₂) 3135(m), 3099(s), 1307(m), 1028(s), 862(s), 771(s), 636(s) C, 49.92(49.82) H, 4.90(5.19) Cl, 24.90(24.60) 24 VPMDC

740, 652, 440 (CHCl₃) 3118(s), 1194(w), 1149(m), 1032(s), 959(w), 843(vs), 638(vs) C, 59.9(61.2) H, 7.5(7.6) Cl, 13.1(13.0) 25 VPMOC

680, 605, 290, 250 (CHCl₃) 2962(m), 2906(s), 2858(m), 1621(w), 1497(m), 1437(s), 1375(vs), 1066(s), 1014(m), 960(m), 943(m), 806(m), 744(m), 700(m) C, 43.29(43.98) H, 5.62(5.54) Cl, 27.54(27.67)

TABLE 5 In Vitro Cytotoxic Activity of Vanadocene Compounds Against Human Cancer Cells. IC₅₀ [MTT](μM) % Apoptosis at 100 μM Compound TERA-2 NTERA-2 U373 NALM-6 TERA-2 NTERA-2 Metallocene Dichlorides HDC >250 >250 >250 N.D. N.D. N.D. MDC >250 >250 >250 N.D. N.D. N.D. TDC >250 >250 >250 N.D. N.D. N.D. ZDC >250 >250 >250 N.D. N.D. N.D. VDC 81 74 42 19 88 (87, 89) 35 (34, 34) Vanadocene Diacido Compounds VDB 154 70 62 17 84 (83, 86) 93 (93, 94) VDI 221 204 5 18 72 (71, 73) 57 (46, 69) VDA 70 68 51 16 85 (78, 92) 85 (78, 93) VDCO 50 90 N.D. N.D. 73 (67, 78) 98 (97, 99) VDCN 51 93 53 N.D. 80 (78, 82) 97 (96, 97) VDOCN 31 63 N.D. N.D. 85 (80, 90) 95 (94, 96) VDSCN 23 17 19 N.D. 64 (58, 69) 53 (46, 60) VDSeCN 9 22 2 3 78 (75, 80) 99.6 ± 0.2 (N = 4) VDFe 100 113 N.D. N.D. 85 (84, 87) 87 (81, 94) VDT 76 137 N.D. N.D. 71 (71, 71) 55 ± 26 (N = 4) Vanadocene Chelated Compounds VD(acac) 64 75 N.D. N.D. 72 ± 17 48 ± 13 (N = 3) VD(bpy) 37 53 N.D. N.D. N.D. 78 (77, 78) VD(dtc) 60 83 7 N.D. 83 (82, 84) 67 ± 13 (N = 3) VD(cat) 79 93 N.D. N.D. N.D. 12 (9, 15) VDPH >250 61 N.D. N.D. 88 ± 3 (N = 3) 90 ± 3 (N = 4) VDH 118 125 >250 N.D. 84 ± 2 (N = 3) 20 ± 5 (N = 3) Substituted Cyclopentadienyl Compounds VMDC 123 86 61 N.D. 45 (27, 61) 13 (13, 14) VPMDC 127 44 172 N.D. 35 (35, 36) 34 (33, 35) VPMOC >250 77 N.D. N.D.  5 (5, 6)  6 (6, 7) Control VDSO₄ >250 >250 N.D. N.D. N.D.

Example 2 Oxovanadium (IV) Compounds

Materials and Methods

The oxovanadium (IV) complexes were synthesized based on previously published chemistry of VO(phen) and VO(phen)₂ complexes. Sakurai, et. al, Biochemical and Biophysical Research Communications, Vol. 206, No. 1, (1995). Selbin, et. al, Chemical Reviews, Vol. 65, No. 2 (1965). Briefly, these complexes were synthesized by reacting an aqueous solution of vanadyl sulfate with an ethanol solution or a chloroform solution of the ligands.

The complexes purified from chloroform, ether and/or water were characterized by Fourier transform infrared spectroscopy (FT-Nicolet model Protege 460; Nicolet Instrument Corp., Madison, Wis.), UV-visible spectroscopy (DU 7400 spectophotometer; Beckman Instruments, Fullerton, Calif.) and elemental analysis (Atlantic Microlab, Inc., Norcross, Ga.). These oxovanadium (IV) complexes have an octahedral or square pyramidal geometry with the oxo ligand (O²⁻) in the axial site. The oxovanadium complexes are stabilized with bidentate ligands which form a 5-membered ring with the vanadium atom. The choice of these three organic ligands (phenanthroline, bipyridyl, bipyrimidal and acetophenone) was based on the reported fact that the cationic oxovanadium(IV) complex of phenanthroline is superior to cisplatin (cis-diamminedichloroplatinum[II]) with respect to antitumor activity, the structural similarity of bipyridyl ring to phenanthroline, as well as the neutral nature of acetophenone complex of oxovanadium(IV).

Structural variations of the ligands included addition of bromo, chloro or methyl groups on the phenanthroline, bipyridyl or acetophenone rings. The chemical structures of the oxovanadium (IV) complexes, including 8 complexes with 1,10-phenanthroline and 4 complexes with 2,2′-bipyridyl, and one neutral complex, bis-5′-bromo-2′-hydroxyacetophenone, are depicted in Table 6. The synthesis and analysis of the compounds can be summarized as follows.

[VO(Phen)(H₂O)₂](SO₄) (Phen=1,10-phenanthroline) (diaqua) (1,10-phenanthroline)oxovanadium(IV) sulfate (Compound 26). A chloroform solution of 1,10-phenanthroline (90.1 mg, 0.5 mmol) was added to VO(SO₄).3H₂O (108.5 mg, 0.5 mmol) in 6 mL of water. The resulting green solution was stirred at room temperature for 3 h, and then stored in refrigerator for one day. The green water layer was separated from the chloroform layer, and water was removed by vacuum. The green solid product (165 mg, 87%) was washed with chloroform and ether, and dried in air. Anal. Calcd for [VO(Phen)(H₂O)₂](SO₄) (C₁₂H₁₂N₂O₇SV): C, 38.01; H, 3.20; N, 7.39. Found: C, 38.57; H, 3.07; N, 7.47. IR spectrum: ν(V═O) 978 cm⁻¹.

[VO(SO₄)(Phen)₂]bis(1,10-phenanthroline)sulfatooxovanadium (IV) (Compound 27). An ethanol solution of 1,10-phenanthroline (180.2 mg, 1.0 mmol) was added to VO(SO₄).3H₂O (108.5 mg, 0.5 mmol) in 6 mL of water. The resulting brown solution was stirred at room temperature for 3 h, and brown microcrystals precipitated from the solution upon standing at −20° C. The product (247 mg, 89%) was washed with chloroform and ether, and dried in air. Anal. Calcd for [VO(SO₄)(Phen)₂].2H₂O (C₂₄H₂₀N₄O₇SV): C, 51.53; H, 3.60; N, 10.01. Found: C, 50.92; H, 3.65; N, 9.87. IR spectrum: ν(V═O) 978 cm⁻¹.

[VO(Me₂-Phen)(H₂O)₂](SO₄) (Me₂-Phen=4,7-dimethyl-1,10-phenanthroline) (diaqua)(4,7-dimethyl-1,10-phenanthroline)oxovanadium(IV) sulfate (Compound 28). A chloroform solution of 4,7-dimethyl-1,10-phenanthroline (104.1, 0.5 mmol) was added to VO(SO₄).3H₂O (108.5 mg, 0.5 mmol) in 6 mL of water resulting in the precipitation of a green solid. The reaction mixture was stirred at room Temperature for one day, and the product (128 mg, 63%) was filtered and washed with water and ether, and dried in air. Anal. Calcd for [VO(Me₂-Phen)(H₂O)₂](SO₄) (C₁₄H₁₆N₂O₇SV): C, 41.29; H, 3.96; N, 6.88. Found: C, 41.08; H, 4.12; N, 6.74. IR spectrum: ν(V═O) 978 cm⁻¹.

[VO(SO₄)(Me₂-Phen)₂]bis(4,7-dimethyl-1,10-phenanthroline) sulfatooxovanadium(IV) (Compound 29) was prepared by mixing an aqueous solution of VO(SO₄).3H₂O (54.3 mg, 0.25 mmol) with an ethanol solution of 4,7-dimethyl-1,10-phenanthroline (104.2 mg, 0.5 mmol) at room temperature. The reaction mixture was stirred at room temperature for 2 days. During this time, the blue solution first turned to green and then to brown. The brown solid product (107 mg, 68%) was obtained by removing solvent and washing with chloroform and ether, and drying under vacuum. Anal. Calcd for [VO(SO₄)(Me₂-Phen)].3H₂O (C₂₈H₃₀N₄O₈SV): C, 53.08; H, 4.77; N, 8.84. Found: C, 53.01; H, 4.58; N, 8.84. IR spectrum: ν(V═O) 973 cm⁻¹.

[VO(Cl-Phen)(H₂O)₂](SO₄) (diaqua)(5-chloro-1,10-phenanthroline) oxovanadium(IV) sulfate (Compound 30) was prepared by mixing an aqueous solution of VO(SO₄).3H₂O (108.5 mg, 0.5 mmol) with an ethanol solution of 5-chloro-1,10-phenanthroline (107.3 mg, 0.5 mmol) at room temperature. The reaction mixture was stirred at room temperature for two days. During this time, the blue solution turned to green. The green solid product (142.3 mg, 69%) was obtained by removing solvent and purifying from water and ether, and drying under vacuum. Anal. Calcd for [VO(Cl-Phen)(H₂O)₂](SO₄) (C₁₂H₁₁N₂O₇ClSV): C, 34.84; H, 2.68; N, 6.77. Found: C, 34.96; H, 2.64; N, 6.84. IR spectrum: ν(V=O) 964 cm³¹ ¹.

[VO(SO₄)(Cl-Phen)₂] (Cl-Phen=5-chloro-1,10- phenanthroline) bis(5-chloro-1,10-phenanthroline)sulfatooxovanadium(IV) (Compound 31). An ethanol solution of 5-chloro-1,10-phenanthroline (214.7 mg, 1.0 mmol) was added to VO(SO₄).3H₂O (108.5 mg, 0.5 mmol) in 6 mL of water. The resulting brown solution was stirred at room temperature for 7 h, and a small amount of brown microcrystals precipitated upon standing at −20° C. The brown solid product (222 mg, 71%) was obtained by removing solvent and washing with chloroform and ether, and drying under vacuum. Anal. Calcd for [VO(SO₄)(Cl-Phen)₂].2H₂O (C₂₄H₁₈N₄O₇Cl₂SV): C, 45.88; H, 2.89; N, 8.92. Found: C, 45.44; H, 2.87; N, 8.75. IR spectrum: ν(V=O) 962 cm⁻¹.

[VO(NO₂-Phen)(H₂O)₂](SO₄) (NO₂-Phen=5-nitro-1,10-phenanthroline) (diaqua)(5-nitro-1,1 0-phenanthroline)oxovanadium (IV) sulfate (Compound 32) was prepared by adding a blue aqueous solution of VO(SO₄).3H₂O (108.5 mg, 0.5 mmol) into a yellow suspension of 5-nitro-1,10-phenanthroline (112.6 mg, 0.5 mmol) in ethanol at room temperature. The reaction mixture turned to green solution immediately, and then was stirred at room temperature for two days. During this time, some brown solid precipitated. The brown solid was filtered off and the filtrate was evaporated to dryness to give rise to a green solid. The green solid product (90.7 mg, 43%) was obtained by purifying from water and ether, and drying under vacuum. Anal. Calcd for [VO(NO₂-Phen) (H₂O)₂](SO₄) (C₁₂H₁₁N₃O₉SV): C, 33.97; H, 2.61; N, 9.91. Found: C, 33.70; H, 2.54; N, 9.78. IR spectrum: ν(V═O) 980 cm⁻¹.

[VO(SO₄)(NO₂-Phen)₂]bis(5-nitro-1,10-phenanthroline) sulfatooxovanadium(IV) (Compound 33) was prepared by mixing a blue aqueous solution of VO(SO₄).3H₂O (108.5 mg, 0.5 mmol) with a yellow suspension of 5-nitro-1,10-phenanthroline (225.2 mg, 1 mmol) in ethanol at room temperature. A brown solution was generated upon the mixing and a yellow solid precipitated gradually. The reaction mixture was stirred at room temperature for one day. The yellow solid product (180 mg, 54%) was obtained by filtration and washing with water, chloroform and ether, and drying in air. Anal. Calcd for [VO(SO₄)(NO₂-Phen)₂].3H₂O (C₂₄H₂₀N₆O₁₂SV): C, 43.18; H, 3.02; N, 12.59. Found: C, 42.61; H, 2.98; N, 12.28. IR spectrum: ν(V═O) 976 cm⁻¹.

[VO(Bpy)(H₂O)₂](SO₄) (Bpy=2,2′-bipyridine) (diaqua)(2,2′bipyridyl) oxovanadium(IV) sulfate (Compound 34). A chloroform solution of 2,2′-bipyridine (78.1 mg, 0.5 mmol) was added to VO(SO₄).3H₂O (108.5 mg, 0.5 mmol) in 6 mL of water. The resulting green solution was stirred at room temperature overnight, and then the water layer was separated from the chloroform layer. The green solid product (105 mg, 59%) was obtained by removing water and washing with ether, and drying in air. Anal. Calcd for [VO(Bpy)(H₂O)₂](SO₄) (C₁₀H₁₂N₂O₇SV): C, 33.81; H, 3.41; N, 7.89. Found: C, 33.77; H, 3.16; N, 7.72. IR spectrum: ν(V═O) 978 cm⁻¹.

[VO(SO₄)(Bpy)₂]bis(2,2′-bipyridyl)sulfatooxovanadium(IV) (Compound 35). An ethanol solution of 2,2′-bipyridine (156.2 mg, 1.0 mmol) was added to VO(SO₄).3H₂O (108.5 mg, 0.5 mmol) in 6 mL of water. The resulting brown solution was stirred at room temperature overnight, and then stored at −20° C. for one day. The brown solid product (180 mg, 76%) was obtained by removing solvent and washing with chloroform, ethanol and ether, and drying in air. Anal. Calcd for [VO(SO₄)(Bpy)₂].H₂O (C₂₀H₁₈N₄O₆SV): C, 48.69; H, 3.68; N, 11.36. Found: C, 48.38; H, 3.81; N, 11.48. IR spectrum: ν(V═O) 978 cm⁻¹.

[VO(Me₂-bpy)(H₂O)₂](SO₄) (Me₂-bpy=4,4′-dimethyl-2,2′-bipyridyl) (diaqua)(4,4′-dimethyl-2,2′-bipyridyl)oxovanadium (IV) sulfate (Compound 36). A chloroform solution of 4,4′-dimethyl-2,2′-bipyridyl (104.1 mg, 0.5 mmol) was added to VO(SO₄).3H₂O (108.5 mg, 0.5 mmol) in 6 mL of water. The reaction mixture was stirred at room temperature for one day, during this time a green solid formed. The product (130 mg, 68%) was filtered and washed with water and ether, and dried in air. Anal. Calcd for [VO(Me₂-bpy)(H₂O)₂](SO₄) (C₁₂H₁₆N₂O₇SV): C, 37.61; H, 4.21; N, 7.31. Found: C, 37.49; H, 4.27; N, 7.16. IR spectrum: ν(V═O) 983 cm⁻¹.

[VO(SO₄)(Me₂-bpy)₂]bis(4,4′-dimethyl-2,2′-bipyridyl) sulfatooxovanadium(IV) (Compound 37). An ethanol solution of 4,4′-dimethyl-2,2′-bipyridyl (92.1 mg, 0.5 mmol) was added to VO(SO₄).3H₂O (54.3 mg, 0.25 mmol) in 6 mL of water. The reaction mixture was stirred at room temperature for 20 h, and a small amount of green solid precipitated. The green solid was removed by filtration. The yellow solid product (72 mg, 51%) was obtained by removing solvent and washing by chloroform and ether, and drying under vacuum. Anal. Calcd for [VO(SO₄)(Me₂-bpy)₂].2H₂O (C₂₄H₂₈N₄O₇SV): C, 50.79; H, 4.97; N, 9.87. Found: C, 50.19; H, 4.81; N, 9.67. IR spectrum: ν(V═O) 978 cm⁻¹.

[VO(Bipym)(H₂O)₂](SO₄) (Bipym=2,2′-bipyrimidine) (diaqua)(2,2′-bipyrimidine) oxovanadium(IV) sulfate (Compound 38) was prepared by mixing an aqueous solution of VO(SO₄).3H₂O (86.8 mg, 0.4 mmol) with an ethanol solution of 2,2′-bipyrimidine (63.3 mg, 0.4 mmol) at room temperature. The reaction mixture was stirred at room temperature for two days. During this time, the blue solution turned to green. The green solid product (112.3 mg, 77%) was obtained by removing solvent and washing with ether, and drying under vacuum. Anal. Calcd for [VO(Bipym)(H₂O)₂](SO₄).0.5H₂O (C₈H₁₁N₄O_(7.5)SV): C, 26.24; H, 3.03; N, 15.30. Found: C, 25.99; H, 2.91; N, 15.20. IR spectrum: ν(V═O) 978 cm⁻¹.

[VO(SO₄)(Bipym)₂]bis(2,2′-bipyrimidine)sulfatooxovanadium(IV) (Compound 39) was prepared by mixing an aqueous solution of VO(SO₄).3H₂O (43.4 mg, 0.2 mmol) with an ethanol solution of 2,2′-bipyrimidine (63.3 mg, 0.4 mmol) at room temperature. The reaction mixture was stirred at room temperature for 5 days, and then kept in refrigerator overnight. During this time, the blue solution turned to green. The green solid product (80 mg, 75%) was obtained by removing solvent and washing with chloroform and ether, and drying under vacuum. Anal. Calcd for [VO(SO₄)(Bipym)₂].3H₂O (C₁₆H₁₈N₈O₈SV): C, 36.03; H, 3.40; N, 21.01. Found: C, 35.83; H, 3.12; N, 21.12. IR spectrum: ν(V═O) 974 cm⁻¹.

[VO(Br,OH-acph)₂] (Br,OH-acph=5′-bromo-2′-hydroxyacetophenone) bis(5′-bromo-2′-hydroxyacetophenone)oxovanadium (IV) (Compound 40). An ethanol solution of 5′-bromo-2′-hydroxyacetophenone (107.6 mg, 0.5 mmol) was added to VO(SO₄).3H₂O (108.5 mg, 0.5 mmol) in water (5 mL). The solution turned to green immediately and a white solid precipitated in a few minutes. After one hour, an aqueous solution of NaOH (20 mg, 0.5 mmol) was added, and the reaction mixture was stirred at room temperature for one day. The resulting yellow solid product (63.5 mg, 40%) was filtered and washed with water and ether, and dried in air. Anal. Calcd for [VO(Br,OH-acph)₂].0.5H₂O (C₁₆H₁₃O_(5.5)Br₂V): C, 38.13; H, 2.60; Br, 31.71. Found: C, 38.18; H, 2.36, Br, 31.65. IR Spectrum: ν(V═O) 971 cm⁻¹. TABLE 6 Oxovanadium(IV) Compounds. UV-vis IR Elemental Analysis λ, nm (ε, M⁻¹cm⁻¹) υV═O, Found (Calcd.) Compound Structure [Solvent] cm⁻¹ C, H, N 26

970(sh), 745(34), 529(21), 432(sh) [H₂O] 978 38.57(38.01), 3.07(3.20), 7.47(7.39) 27

712(33), 540(sh), 436(sh) [H₂O] 978 50.92(51.53), 3.65(3.60), 9.87(10.01) 28

ND 978 41.08(41.29), 4.12(3.96), 6.74(6.88) 29

664(83), [H₂O]765(37), 448(236) [DMSO] 973 53.01(53.08), 4.58(4.77), 8.84(8.84) 30

745(30), 523(18), 438(sh), [H₂O] 964 34.96(34.84), 2.64(2.68), 6.84(6.77) 31

685(58), 535(sh), 446(sh), [H₂O] 962 45.44(45.88), 2.87(2.89), 8.75(8.92) 32

746(34), 444(sh) [H₂O] 980 33.70(33.97), 2.54(2.61), 9.78(9.91) 33

757(34), 459(sh) [DM50] 976 42.61(43.18), 2.98(3.02), 12.28(12.59) 34

968(sh), 749(23), 535(sh), [H₂O] 978 33.77(33.81), 3.16(3.41), 7.72(7.89) 35

726(27), 533(19), 453(sh), [H₂O] 978 48.43(48.69), 3.81(3.68), 11.48(11.36) 36

ND 983 37.49(37.61), 4.27(4.21), 7.16(7.31) 37

701(51), 535(49) [H₂O] 978 150.19(50.79), 4.81(4.97), 9.67(9.87) 38

752(23), 572(sh), 406(sh), [H₂O] 978 25.99(26.24), 2.91(3.03), 15.20(15.30) 39

753(23), 564(sh), 410(sh), [H₂O] 974 35.83(36.03), 3.12(3.40), 21.12(21.01) 40

833(55), 621(62), 502(185) [DMSO] 971 C, 38.18(38.13), H, 2.36(2.60), Br, 31.65(31.71) Cell Lines and Culture Conditions

Human testicular cancer cell lines, Tera-2 (embryonal carcinoma) and Ntera-2 (pluripotent embryonal carcinoma) were obtained from the American Type Culture Collection (ATCC) (Rockeville, Md.) and propagated in T-25, T-75, or T-150 cm² tissue culture flasks (Corning Corp., Corning, N.Y.) in McCoy's 5A medium and Dulbecco's modified Eagle's medium respectively. Both media were supplemented with 10% fetal calf serum (FCS), 4 mM glutamine, 100 U/ml penicillin G, and 100 mg/ml streptomycin sulfate. All tissue culture reagents were obtained from Life Technologies Inc. (GIBCO-BRL), Gaithersburg, Md. Cell lines were cultivated for a minimum of two passages after thawing prior to experimentation. Other cell lines that were used in this study were the human B-lineage acute lymphoblastic leukemia (ALL) cell line NALM-6. Uckun, F. M., Evans, W. E., Forsyth, C. J., Waddick, K.G., Tuel-Ahlgren, L., Chelstrom, L. M., Burkhardt, A., Bolen, J., Myers, D. E. Biotherapy of B-cell precursor leukemia by targeting genistein to CD19-associated tyrosine kinase. Science (Washington D.C.) 267.886-91, 1995; T-lineage ALL cell line MOLT-3, Waurzyniak, B., Shneider, E. A., Tumer, N., Yanishevski, Y., Gunther, R., Chelstrom, L., Wendorf, H., Myers, D. E., Irvin, J. D., Messinger, Y., Ek, O., Zeren, T., Chandan-Langlie, M., Evans, W. E., Uckun, F. M. In vivo toxicity, pharmacokinetics, and antileukemic activity of TXU (anti-CD7)-pokeweed antiviral protein immunotoxin. Clinical Cancer Research 3:881-890, 1997; AML cell line HL-60, Perentesis, J. P., Waddick, K. G., Bendel, A. E., Shao, Y., Warman, B. E., Chandan-Langlie, M., and Uckun, F. M. Induction of apoptosis in multi-drug resistant andradiation-resistant acute myeloid leukemia cells by a recombinant fusion toxin directed against the granulocyte macrophage colony stimulating factor receptor. Clin. Cancer Res. 3:347-355, 1997; breast cancer cell lines MDA-MB-23 land BT-20, Uckun, F. M., Narla, R. K., Jun, X., Zeren, T., Venkatachalam, T., Waddick, K. G., Rostostev, A., Myers, D. E. Cytotoxic activity of EGF-genstein against breast cancer cells. Clin. Cancer Res. 4:901-912, 1998; glioblastoma cell lines U87 and U373, Narla, R. K., Liu, X., Myers, D. E., and Uckun, F. M. 4-(3′-Bromo-4′hydroxylphenyl)-amino-6,7-dimethoxyquinazoline (WHI-P154): A novel quinazoline derivative with potent cytotoxic activity against human glioblastoma cells. Clin. Cancer Res. 4:1405-1414, 1998.

MTT Assays.

MTT (3-[4,5-dimethyl thiazol-2-yl]-2,5-diphenyltetrazolium bromide)-based colorimetric assays were used for evaluation of the cytotoxicity of vanadocene compounds. Mosmann, T. Rapid calorimetric assay for cellular growth and survival: application to proliferation and cytotoxicity assays. J. Immunol. Methods, 65: 55-63, 1983. Briefly, cells were harvested with 0.125% (w/v) trypsin-0.02% EDTA (GIBCO-BRL) from exponential-phase maintenance cultures and centrifuged (300 g×5 min). After suspension and counting, cells were dispensed within triplicate 96-well tissue culture plates in 100 μl volumes. After 24 h incubation, the culture medium was discarded and replaced with 100 μl of fresh medium containing serial two-fold dilutions of drugs in medium to yield 1.9 μM to 250 μM. All compounds were reconstituted in DMSO to a concentration of 100 mM, and the stock solution was made fresh for each experiment. Control wells consisted of medium containing 0.25% of DMSO alone were used for solvent control. Culture plates were then incubated for 24 h before adding 10 μl of MTT solution (5 mg/ml in PBS) to each well. Wells containing only medium and MTT were used as controls for each plate. The tetrazolium/formazan reaction was allowed to proceed for 4 h at 37° C., and then 100 μl of the solubilization buffer (10% sodium dodecyl sulfate in 0.1% HCl) were added to all wells and mixed thoroughly to dissolve the dark blue formazan crystals. After an overnight incubation at 37° C., the optical densities at 540 nm were measured using a 96-well multiscanner autoreader, with the solubilization buffer serving as blank. All assays were run in triplicate and results were expressed as IC₅₀ values. The IC₅₀ was defined as the concentration required for 50% reduction of the optical density in each test, and was calculated as: (A₅₄₀ of drug-treated wells—A₅₄₀ of control wells)/A₅₄₀ of drug-free wells×100.

Adhesion assays

In vitro adhesion assays, Narla R K, Liu X P, Klis D, Uckun F M. Inhibition of human glioblastoma cell adhesion and invasion by 4-(4′-hydroxylphenyl)-amino-6,7-dimethoxyquinazoline (WHI-P131) and 4-(3′-bromo-4′-hydroxylphenyl)-amino-6,7-dimethoxyquinazoline (WHI-P154). Clin Cancer Res 4:2463-71, 1998, were performed to (a) study the baseline adhesive properties of U373 glioblastoma and TERA-2 testicular cancer cell lines and (b) evaluate the effects of VDC and VDSeCN derivatives on the adhesive properties of U373 glioblastoma and TERA-2 testicular cancer cells. The plates for the adhesion assays were precoated with the extracellular matrix proteins laminin, fibronectin or type IV collagen (each at a final concentration of 1 μg/ml in PBS) overnight at 4° C. and dried. On the day of the experiment, the wells were rehydrated and blocked with 10% bovine serum albumin in PBS for 1 hr at room temperature and used for the adhesion assays, as described below. To study the effects of VDC and VDSeCN on cancer cell adhesion, exponentially growing cells in DMEM were incubated with these compounds at concentrations ranging from 1 μM to 10 μM for 16 hr in a humidified 5% CO₂ atmosphere. DMSO (0.1%) was included as a vehicle control. After treatment, cells were detached from the flasks with 0.05% trypsin (Life Technologies) resuspended in DMEM, incubated at 37° C. for 2 hr to allow them to recover from the trypsinization stress and examined for their ability to adhere to plates precoated with ECM proteins.Cells were centrifuged, washed twice with serum-free DMEM, counted and resuspended in serum-free DMEM to a final concentration of 2.5×10⁵ cells/ml. One hundred μl of the cell suspension containing 2.5×10⁴ cells were added to each well and cells were allowed to adhere for 1 hr at 37° C. in a humidified 5% CO₂ atmosphere. The non-adherent cells were removed by gently washing the cells with PBS and then the adherent fraction was quantitated using MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide) assays as described above. The adherent fractions of cells treated with VDC or VDSeCN were compared to those of DMSO treated control cells and the percent inhibition of adhesion was determined using the formula: % Inhibition=100× (1-Adherent Fraction of Drug-Treated Cells/Adherent Fraction of Control Cells). Each treatment condition was evaluated in duplicate in 3 independent experiments. The IC₅₀ values were calculated by non-linear regression analysis using an Graphpad Prism software version 2.0 (Graphpad Software, Inc., San Diego, Calif.).

Cytotoxicity of Oxovanadium Compounds Against Human Cancer Cell Lines

A series oxovanadium (IV) complexes (Table 6) were prepared, including eight phenanthroline (phen)-linked [VO(phen), VO(phen))₂, VO(Me₂-phen), VO (Me₂-phen)₂, VO(Cl-phen), VO(Cl-phen)₂, VO(NO₂-phen), VO(NO₂-phen)₂] and six bipyridyl (bipy)-linked [VO(bipy), VO(bipy))₂, VO(Me₂-bipy) VO(Me₂-bipy)₂, two bipyramide VO, and two bipyramide VO₂, and one acetophenone (acph)-linked [VO(Br,OH-acph)₂] and tested their cytotoxic activity against 14 different human cancer cell lines, including the B-lineage ALL cell line NALM-6, T-lineage ALL cell line MOLT-3, AML cell line HL-60, multiple myeloma cell lines ARH-77, U266BL, and HS-SULTAN, Hodgkin's lymphoma cell line HS445, and the testicular cancer cell lines 833K, 64cp5, TERA-2, and NTD1, prostate cancer cell line PC3, breast cancer cell line BT-20, and glioblastoma cell line U373 using MTT assays and/or confocal laser scanning microscopy. Each compound was tested side-by-side at eight different concentrations in the range of 0.1-250 μM.

Each of the 15 oxovanadium complexes exhibited significant cytotoxicity against several of the cancer cell lines in a concentration-dependent fashion (Table 7, FIG. 1). FIG. 1 shows the concentration-dependent MTT-based cytotoxicity curves of 12 representative oxovanadium (IV) compounds against NALM-6 leukemia cells. The cytotoxic activity of the oxovanadium (IV) complexes was strongly dependent on the type of coordinated heteroligands. When compared with diaqua mono-chelated complexes, the butterfly structure oxovanadium complexes stabilized with 5-membered bis-chelated ligands of phenanthroline or bipyridyl showed superior cytotoxic activity against cancer cells. The mono-chelated [VO(Me₂-phen)=compound 28] as well as bis-chelated-1,10-phenantroline complexes [VO(Me₂-phen)₂=compound 29] were the most potent oxovanadium compounds and killed each of the 7 cell lines examined at low micromolar concentrations (Table 7). Notably, the dimethyl substitution of the phenanthroline rings is believed to be significant for the anti-cancer activity of both compounds (29) [=VO(Me₂-phen)₂] and (28) [VO(Me₂-phen)] because unsubstituted bis-chelated and mono-chelated 1,10-phenanthroline oxovanadium (IV) complexes [VO(phen)=compound 276 or VO(phen)₂=compound 27] were less active. Addition of a chloro or nitro group to the 1,10-phenanthroline complexes did not significantly improve the cytotoxic activity of the unsubstituted oxovanadium (IV) complexes (Table 7). Irrespective of the ligands, bis-chelated phenanthroline containing compounds showed better activity than the mono-chelated phenanthroline containing complexes. The marked differences in the cytotoxic activity of oxovanadium (IV) complexes containing different heterocyclic ancillary ligands suggest that the cytotoxic activity of these compounds is determined by the identity of the 5-membered bidentate ligands as well as the nature of the substitutents on the heterocyclic aromatic rings. The ability of oxovanadium compounds to inhibit the in vitro clonogenic growth of NALM-6 leukemia cells was also investigated. As detailed in Table 8, compounds 28 and 29 were the most potent compounds against clonogenic NALM-6 cells and completely abrogated in vitro colony formation at concentrations <1 μM.

Oxovanadium (IV) Compounds Induce Apoptosis in Human Cancer Cells

In order to determine if the cytotoxicity of the oxovanadium compounds is associated with apoptotic cell death, 64cp5 and 833-K testicular cancer cells were cultured with the oxovanadium compounds (50 μM) for 24 h and then subjected to flow cytometric analysis for dUTP incorporation by the TdT-mediated TUNEL assay. FIG. 2A depicts the two-color flow cytometric contour plots of cells from representative TUNEL assays. Control 64cp5 and 833-K cells were treated for 24 hours at 37° C. with 0.1% DMSO whereas test cells were treated for 24 hours at 37° C. with an oxovanadium compound at 50 μM final concentration. The TdT-dependent incorporation of FITC-dUTP was dramatically increased in cells treated with the oxovanadium compounds as a result of abundance of free 3′-hydroxyl DNA ends created by endonuclease-mediated DNA fragmentation. Among the 15 vanadocenes evaluated by the flow cytometric TUNEL assay, 8 caused a marked increase in TUNEL-positive nuclei ranging from 50.8% to 76.1% for 64cp5 cells and 63.5% to 82.2% for 833-K cells respectively (FIG. 2B). Apoptosis after treatment with oxovanadium compounds was also evident from the concentration-dependent emergence of a hypodiploid (<2N) peak in the DNA histograms of PI-stained cells, which was accompanied by nonselective loss of G0/1, S, and G2M phase cells (FIG. 2). Similar results were obtained with NALM-6 leukemia and HS-SULTAN multiple myeloma cells (Table 9, FIG. 3). As evidenced by the confocal laser scanning microscopy images depicted in FIG. 5, VO(Me₂-phen)₂ (compound 29) and VO(Me₂-phen) (compound 28) treated [but not VO(Cl-phen)₂ (=compound 31 )-treated] leukemic NALM-6 and HS-SULTAN cells examined for FITC-conjugated dUTP incorporation (green fluorescence) and propidium iodide counterstaining (red fluorescence) showed many apoptotic yellow nuclei with superimposed green and red fluorescence at 48 hours after treatment. limmunofluorescence staining with anti-α-tubulin antibody and the nuclear dye toto-3 in combination with confocal laser scanning microscopy was used to examine the morphological features of cancer cells treated with oxovanadium compounds. FIG. 4 depicts the two-color confocal microscopy images of BT-20 breast cancer, PC3 prostate cancer, and U373 glioblastoma cells after treatment with oxovanadium compounds. Most of the oxovanadium-treated cells displayed the characteristic morphologic features of apoptotic cell death, including an abnormal architecture with complete disruption of microtubules, marked shrinkage, chromatin condensation, nuclear fragmentation, the appearance of typical apoptotic bodies and inability to adhere to the substratum.

In order to test whether oxovanadium compounds induce apoptosis by altering the mitochondrial transmembrane potential, NALM-6 leukemia cells were exposed to compound (29) for apoptosis-associated changes in mitochondrial membrane potential (ΔΨ) and mitochondrial mass using specific fluorescent mitochondrial probes and multiparameter flow cytometry. To measure changes in ΔΨ, DilC1 (which accumulates in energized mitochondria) was used, whereas the mitochondrial mass was determined by staining the cells with NAO, a fluorescent dye that binds to the mitochondrial inner membrane independent of energetic state. Treatment of NALM-6 leukemia cells with compound 29 for 24 h-72 h increased the number of depolarized mitochondria in a concentration- and time-dependent fashion, as determined by flow cytometry using DiIC1 (27-29) (FIG. 5A). As shown in FIG. 5A, the fraction of DiIC1-negative cells with depolarized mitochondria increased from 6.5% in vehicle treated control cells to 91.5% in cells treated with 1 μM compound 29 for 48 hours. The average EC₅₀ values for compound (29) induced depolarization of mitochondria, as measured by decreased DiIC1 staining were 3.6 μM, 0.3 μM and 0.08 μM for 24 hr 48 hr and 72 hr treatment respectively. The observed changes in ΔΨm were not due to loss in mitochondrial mass, as confirmed by a virtually identical staining intensity of NAO in the treated and untreated NALM-6 cells (FIG. 5B). To further confirm this relative change in ΔΨm, JC-1, a mitochondrial dye, which normally exists in solution as a monomer emitting green fluorescence and assumes a dimeric configuration emitting red fluorescence in a reaction driven by mitochondrial transmembrane potential was used. Thus, the use of JC-1 allows simultaneous analysis of mitochondrial mass (green fluorescence) and mitochondrial transmembrane potential (red/orange fluorescence). After treatment of NALM-6 cells with compound 29 at increasing concentrations ranging from 500 nM to 1 μM and with increasing duration of exposure of 24 h or 48 h, a progressive dissociation between ΔΨm and mitochondrial mass was observed, with decrement in JC-1 red/orange fluorescence without a significant corresponding drop in JC-1 green fluorescence. The fraction of JC-1 red/orange fluorescence-positive cells decreased from 98.6% in vehicle-treated control cells to 56.1% in cells treated with 500 nM of compound 29 for 48 hr and 8.4% in cells treated with 500 nM of compound 29 for 72 hr. The average EC₅₀ for compound 29-induced depolarization of mitochondria, as measured by JC-1 red/orange fluorescence were 4.2 μM for the 24 hr treatment and 0.5 μM for the 48 hr treatment. These results collectively demonstrate that compound 29 causes a significant decrease in mitochondrial transmembrane potential in NALM-6 human leukemia cells.

The results indicate that oxovanadium (IV) complexes with 1,10-phenanthroline, 2,2′-bipyridyl, or 5′-bromo-2′-hydroxyacetophenone and their derivatives linked to vanadium(IV) via nitrogen or oxygen atoms have potent anti cancer activity against human cancer cells. The order of efficacy for the 15 oxovanadium (IV) complexes against NALM-6 leukemia cells as follows: VO (Me₂-phen)₂>VO(NO₂-phen)>VO(Me₂-phen)>VO(phen))₂,>VO(Cl-phen)₂>VO(phen)>VO(Cl-phen)>VO(Me₂-bipy)₂>VO(N₂-phen)>VO(Me₂-bipy)>VObipym>VObipym₂>VO(bipy)>VO(bipy)₂>VO(Br,OH-acph)₂.

Apoptosis induction of cytotines of the oxovanadium compounds of the present invention extend to human sperm. Therefore, these compounds are also useful as sperm or birth control. TABLE 7 Cytotoxic of Activity Oxovanadium(IV) Compounds Against Leukemia, Hodgkin's Lymphoma and Multiple Myeloma Cells NALM-6 MOLT-3 HS445 HL-60 U266BL ARH77 HS-SULTAN Compound IC₅₀ (μM) IC₅₀ (μM) IC₅₀ (μM) IC₅₀ (μM) IC₅₀ (μM) IC₅₀ (μM) IC₅₀ (μM) 26 3.4 ± 0.2 2.7 ± 0.2 6.3 ± 1.8  3.2 ± 1.1  3.5 ± 0.5 15.6 ± 3.2 11.2 ± 2.2 27 0.97 ± 0.1   1.4 ± 0.04 5.8 ± 1.2  4.6 ± 1.4  2.2 ± 0.6  3.3 ± 0.8  4.4 ± 0.8 28 0.78 ± 0.1  1.37 ± 0.07 3.3 ± 1.4  6.2 ± 2.3  1.3 ± 0.1  8.1 ± 1.6  5.1 ± 1.02 29  0.2 ± 0.03 0.19 ± 0.01  0.5 ± 0.08 0.98 ± 0.1  0.5 ± 0.02 0.81 ± 0.9  0.8 ± 0.05 30  3.6 ± 0.07  3.4 ± 0.03 7.5 ± 2.5 15.3 ± 4.9  8.5 ± 1.2 30.3 ± 5.6  9.9 ± 5.4 31  1.6 ± 0.03 2.1 ± 0.2 5.2 ± 1.1  5.3 ± 1.8  3.7 ± 1.1 10.5 ± 3.8  5.8 ± 0.6 32 4.1 ± 0.4 2.3 ± 0.3 9.1 ± 2.5  4.9 ± 1.2 18.1 ± 5.1  5.4 ± 1.5 14.5 ± 2.5 33  0.7 ± 0.01  1.4 ± 0.06 2.3 ± 0.6  2.6 ± 0.4  7.2 ± 1.1  5.7 ± 1.3 13.8 ± 3.6 34 14.9 ± 0.6  13.1 ± 1.1  41.7 ± 5.4  >100 30.4 ± 7.8 >100 62.8 ± 2.3 35 15.5 ± 3.8  14.2 ± 3.8  21.6 ± 4.3  31.4 ± 6.9 32.1 ± 5.2 26.8 ± 5.4 35.4 ± 3.3 36 8.5 ± 0.5 8.2 ± 0.5 27.8 ± 3.4  38.6 ± 4.5 38.4 ± 3.2 >100 65.1 ± 6.1 37 3.9 ± 0.3 4.8 ± 0.3 12.6 ± 3.3  28.4 ± 3.8 13.3 ± 5.1 58.3 ± 6.8 11.4 ± 2.2 38 12.1 ± 1.6  27.7 ± 2.5  96.5 ± 8.6  >100 91.2 ± 9.9 >100 >100 39 12.2 ± 2.3  35.1 ± 4.7  98.4 ± 9.1  >100 99.1 ± 8.1 >100 >100 40 17.4 ± 0.9  41.8 ± 3.9  96.5 ± 6.4  >100 98.1 ± 6.7 >100 78.4 ± 5.8 Cells were treated with various concentrations ranging from 0.1 μM to 100 μM of oxovanadium(IV) complexes for 48 hr and the cell survival was measured with MTT assays and EC₅₀s were calculated with non-linear regression analysis.

TABLE 8 Cytotoxic Activity of Oxovanadium (IV) Compounds Against Testicular cancer, Brain tumor, Breast Cancer and Prostate Cancer cells Compound 833-K 64cp5 TERA-2 NTD1 U373 BT20 PC3 26 12.8 8.5 >100 >100 7.7 6.6 11.2 27 7.5 18.5 37.6 >100 6.8 7.2 10.8 28 6 15.2 57.6 12.8 2.2 2.1 5.8 29 0.85 0.75 19.5 10.8 1.8 1.5 1.7 30 12.8 10.9 18.1 >100 22.4 18.2 12.4 31 4.6 >100 24.2 50.1 6.3 5.4 4.6 32 11.5 25.4 7.2 20.2 20.5 13.7 12.9 33 1.1 5.9 2.6 9.1 7.2 5.6 6.1 34 >100 >100 >100 >100 58.4 51.2 55.8 35 96.2 >100 >100 >100 >100 70.8 56.2 36 >100 >100 >100 >100 >100 >100 N.D. 37 34.9 >100 >100 >100 25.6 15.7 N.D. 38 >100 >100 74.3 >100 >100 >100 N.D. 39 >100 >100 >100 >100 >100 >100 N.D. 40 >100 >100 35.4 >100 >100 >100 N.D.

Example 3

The following illustrate representative pharmaceutical dosage forms, containing a compound of formula I (‘Compound X’), for therapeutic or prophylactic use in humans. (I) Tablet 1 mg/tablet ‘Compound X’ 100.0 Lactose 77.5 Povidone 15.0 Croscarmellose sodium 12.0 Microcrystalline cellulose 92.5 Magnesium stearate 3.0 300.0

(ii) Tablet 2 mg/tablet ‘Compound X’ 20.0 Microcrystalline cellulose 410.0 Starch 50.0 Sodium starch glycolate 15.0 Magnesium stearate 5.0 500.0

(iii) Capsule mg/capsule ‘Compound X’ 10.0 Colloidal silicon dioxide 1.5 Lactose 465.5 Pregelatinized starch 120.0 Magnesium stearate 3.0 600.0

(iv) Injection 1 (1 mg/ml) mg/ml ‘Compound X’ (free acid form) 1.0 Dibasic sodium phosphate 12.0 Monobasic sodium phosphate 0.7 Sodium chloride 4.5 1.0 N Sodium hydroxide solution q.s. (pH adjustment to 7.0-7.5) Water for injection q.s. ad 1 mL

(v) Injection 2 (10 mg/ml) mg/ml ‘Compound X’ (free acid form) 10.0 Monobasic sodium phosphate 0.3 Dibasic sodium phosphate 1.1 Polyethylene glycol 400 200.0 01 N Sodium hydroxide solution q.s. (pH adjustment to 7.0-7.5) Water for injection q.s. ad 1 mL

(vi) Aerosol mg/can ‘Compound X’ 20.0 Oleic acid 10.0 Trichloromonofluoromethane 5,000.0 Dichlorodifluoromethane 10,000.0 Dichlorotetrafluoroethane 5,000.0 The above formulations may be obtained by conventional procedures well known in the pharmaceutical art.

All publications, patents, and patent documents are incorporated by reference herein, as though individually incorporated by reference. The invention has been described with reference to various specific and preferred embodiments and techniques. However, it should be understood that many variations and modifications may be made while remaining within the spirit and scope of the invention. 

1. A compound of formula V:

wherein R⁷ and R⁹ are each independently H, (C1-C3)alkyl, (C1-C3)alkoxy, or halo(C₁-C3)alkyl; R⁸ is H, (C1-C3)alkyl, halo, (C1-C3)alkoxy, or halo(C1-C3)alkyl; Y and Y¹ are each independently a monodentate or bidentate ligand; and n is 0 or 1; or a pharmaceutically acceptable salt thereof.
 2. A compound of formula VII:

wherein R¹ and R² are each independently a cyclopentadienyl ring, wherein any cyclopentadienyl ring may optionally be substituted with one or more (C1-C3)alkyl; and R¹⁰-R¹³ are each independently H, halo, or (C1-C6)alkyl; or a pharmaceutically acceptable salt thereof.
 3. A compound which is [VO(Bipym)(H₂O)₂](SO₄), [VO(SO₄)(Bipym)₂] or [VO(Br,OH-acph)₂].
 4. A method for treating cancer in a mammal comprising administering to the mammal in need of such treatment an effective amount of a vanadium (IV) compound; or a parmaceutically acceptable salt thereof; with the proviso that the vanadium (IV) compound is not VCp₂Cl₂ or [VO(Phen)(H₂O)₂](SO₄).
 5. The method of claim 4 wherein the vanadium (IV) compound is a compound of formula I:

wherein, R₁-R₂ are each independently halo, OH₂, O₃SCF₃, N₃, CN, OCN, SCN, or SeCN; and R₃-R₄ are each independently a cyclopentadienyl ring, wherein each cyclopentadienyl ring is optionally substituted with one or more (C1-C3)alkyl.
 6. The method of claim 4 wherein the vanadium (IV) compound is a compound of formula II:

wherein R and R¹ are each independently H, (C1-C3)alkyl, halogen, (C1-C3)alkoxy, halo(C1-C3)alkyl, cyano, (C₂-C₆)alkanoyloxy or nitro; X and X¹ are each independently monodentate or bidentate ligands, or no ligand is present on X¹; and Y is a monodentate ligand.
 7. The method of claim 4 wherein the vanadium (IV) compound is a compound of formula III:

wherein R² and R³ are each independently H, (C1-C3)alkyl, halogen, (C1-C3)alkoxy, halo(C1-C3)alkyl, cyano, (C₂-C₆)alkanoyloxy or nitro; X² and X³ are each independently monodentate or bidentate ligands; or no ligand is present on X³; and Z is selected from O, CH₂, CH₂—CH₂ and CH═CH.
 8. The method of claim 4 wherein the vanadium (IV) compound is a compound of formula IV:

wherein R⁴, R⁵ and R⁶ are each independently H, (C1-C3)alkyl, halogen, (C1-C3)alkoxy, halo(C1-C3)alkyl, cyano, (C₂-C₆)alkanoyloxy or nitro; and X⁴ and X⁵ are each independently a monodentate or bidentate ligand, or no ligand is present on X⁵; and Y is a monodentate ligand.
 9. The method of claim 5 wherein the compound of formula I is VCp₂Cl₂, VCp₂Br₂, VCp₂I₂, VCp₂X₂, VCp₂(N₃)₂, VCp₂(CN)₂, VCp₂(NCO)₂, VCp₂(NCO)Cl, VCp₂(NCS)₂.0.5H₂O, VCp₂(NCSe)₂, VCp₂Cl (CH₃ CN)(FeCl₄), VCp₂(O₃SCF₃)₂, V(MeCP)₂Cl₂.0.5 H₂O, V(Me₅CP)₂Cl₂, VCp₂(acac), VCp₂(hf-acac), VCp₂(bpy), VCp₂(cat), VCp₂(dtc), VCp₂PH, VCp₂H, [VO(Bpy)(H₂O)₂](SO₄), [VO(SO₄)(Bpy)₂], [VO(Me₂-bpy)(H₂O)₂](SO₄), [VO(SO₄)(Me₂-bpy)₂], [VO(Bpy)(H₂O)₂](SO₄), [VO(SO₄)(Bpy)₂], [VO(Me₂-bpy)(H₂O)₂](SO₄), [VO(SO₄)(Me₂-bpy)₂], [VO(Phen)(H₂O)₂](SO₄), [VO(SO₄)(Phen)₂], [VO(Me₂-Phen)(H₂O)₂](SO₄), [VO(SO₄)(Me₂-Phen)₂], [VO(Cl-Phen)(H₂O)₂](SO₄), [VO(SO₄)(Cl-Phen)₂], [VO(N₂-Phen)(H₂O)₂](SO₄), [VO(SO₄)(NO₂-Phen)₂], [VO(Bpy)(H₂O)₂](SO₄), [VO(SO₄)(BPY)₂], [VO(Me₂-bpy)(H₂O)₂](SO₄), [VO(SO₄)(Me₂-bpy)₂], [VO(Phen)(H₂O)₂](SO₄), [VO(SO₄)(Phen)₂], [VO(Me₂-Phen)(H₂O)₂](SO₄), or [VO(SO₄)(Me₂-Phen)₂].
 10. The method of claim 4 wherein the cancer is testicular cancer, Hodgkin's lymphoma, multiple myeloma, or non-Hodgkin's lymphoma.
 11. A method for treating a mammal inflicted with cancer comprising administering to the mammal in need of such treatment an effective amount of an oxovanadium compound; or a pharmaceutically acceptable salt thereof; with the proviso that the cancer is not pharyngonasal cancer.
 12. A method for treating a mammal inflicted with cancer comprising administering to the mammal in need of such treatment an effective amount of a vanadocene compound; or a pharmaeutically acceptable salt thereof; with the proviso that the vanadocene compound is not VCp₂Cl₂. 